The CWU said that proposals by T-Mobile to overhaul performance related bonuses worth up to £1000 per employee could lead to a serious loss of earning potential for many staff members.
CWU telecoms organiser Nick Childs said: "What is currently being proposed would be to the financial detriment of the vast majority of our T-Mobile membership. We will challenge both the proposal and the transparency of the consultation currently in progress. We will also support any member who wants to take out a grievance about the impact T-Mobile´s proposals would have on them."
T-Mobile said that the performance bonuses had been replaced not scrapped. It said that employees had better ability to earn higher bonuses under the pay review.
A T-Mobile spokeswoman said: "Following full consultation T-Mobile has replaced existing bonus arrangements for customer services advisers with a new scheme. This increases the employee´s opportunity to earn higher-level bonuses."
Separately trade unions representing O2 staff recommended that O2 members accept O2´s latest pay proposals. Unions started to ballot members last week.
Assistant secretary and lead negotiator Grace Mitchell said: "We´d have liked a bit more but have accepted that this is the best offer we can reach through negotiation."
An O2 spokesman said: "The trade unions will recommend the proposals and consult with their members. We expect the results back in the middle of the month."
O2 shop staff will see a consolidated pay rise of between two and nine per cent with most retail grades receiving six per cent or more.

The measure was revealed in last month´s Budget statement by Chancellor Gordon Brown.
He said: "The measure will only be exercised where Customs has reasonable grounds to believe that the additional records might assist in identifying supplies on which VAT might go unpaid. This fraud most commonly arises from supplies of mobile phones and computer chips."
The measure is intended to stamp out VAT fraud and organised crime.
Thefts of large consignments of mobile phones have increased dramatically in recent months. Metropolitan Police detective inspector Paul Douglas told Mobile News that most thefts are either carried out to set up a VAT fraud or to remove Customs-stamped boxes from a supply chain.
"These kinds of attacks are fuelling VAT fraud" he said.
The Budget confirmed the right of Customs officers to apply date stamps to goods and to record goods by scanning them.
Until now insurance companies have not required traders to record IMEI numbers. Royston Ford a surveyor and investigator at Cunningham Lindsay loss adjusters said that insurers have started making losses on the mobile phone trade and have pushed for a policy change on the recording of IMEI numbers.
"The vast majority of policies issued to mobile phone traders have had no requirements whatsoever for IMEI retention" said Ford.
"A certain level of risk management is OK for insurers as long as they are making money. But as soon as they start to lose money insurers will look at their policies again. That´s the bottom line."
The Budget report stated: "The measure will supplement Customs´ existing power to specify record-keeping requirements for all businesses of a particular description. It will enable record-keeping requirements to be imposed where they are necessary to help combat fraud."
See crime feature page 30

Orange has signed 16 direct dealers up to the new scheme. Approved dealers will receive an ongoing revenue share based on customer spend and have exclusive access to generic SIM-free stock approved by Orange.
Dealers will also have first access to Orange Broadband which will be re-branded from Wanadoo on June 1 and Orange Landline which will be re-branded from Equant in Q3.
To make the cut Orange connections have to make up 30 per cent of a dealer´s total business and dealers have to connect 120 contract customers a month. Dealers also have to deliver customers that earn Orange £190 in profit over their tenure.
Twelve of the 16 specialist partners have also qualified to enter a dedicated tier for Orange b2b dealers called the Orange Business Specialist Partner Programme. Dealers have to connect a minimum of 100 business customers to contract tariffs in order to become specialist business partners.
Orange´s long-running Orange Business Specialist (OBS) scheme which counts 26 dealers among its members will run alongside the new specialist programmes until the end of the year when it will be made redundant. Orange head of dealer and distribution Chris Hough expects all current OBS dealers to hit targets and migrate to the new specialist scheme by January 1 2007.
Dealer performance will be monitored on a quarterly basis with opportunities to migrate in July October and January. OBS dealers that do not hit Orange´s minimum targets by January 1 will have their privileges revoked.
Over the next month Orange will examine data it has compiled about all Orange dealers and choose which to retain and which to fire.
Hough told Mobile News that Orange has accumulated customer lifetime value data which tells the network how much profit it makes on each customer for both direct and third-party connections.
Mobile News understands that Orange will use the data to set targets for dealers dropping dealers that do not meet the targets.
The new ongoing revenue share pays five per cent on total revenues for a customer between month six and 12 of their contract 7.5 per cent between month 12 and 24 and 10 per cent on customers who have been with Orange longer than 24 months.
Orange will only pay ongoing revenues to dealers for customers who sign up after April 1 until Orange´s back-office systems are brought in line with the new pay policy.
"We are putting a technical fix in place so we can pay dealers for their existing base too but that won´t be ready until Q3" admitted Hough.
"But this is a big bonus for these guys because they will get a monthly payment for the time that a customer stays with the network."

A T-Mobile spokeswoman said: "We have had an issue with SIM cards because of the popularity of Flext. But we have just increased the order of SIM cards and the situation should be sorted out this week."
Hugh Symons business manager Bob Sweetlove said: "There have been shortages across all T-Mobile´s routes to market but I understand it is going to sort it out."
Dealers complained of severe shortages of Nokia 6111s and MDA Varios.
The T-Mobile spokeswoman said: "We knew it was going to be a popular price plan but we hadn´t anticipated just how popular. I can´t give a figure for shortages. There have also been delays with the Nokia 6111 because of its popularity on Flext but these have been addressed."
The Carphone Warehouse has withdrawn its promotional offer of half-price line rental on T-Mobile´s £35 Flext tariff.
A spokesman said: "The £17.50 promotional tariff has come to an end after six weeks as with a lot of introductory tariffs for all networks. But Flext is still very popular."

The ICT Council is one of the top level FEI committees responsible for identifying and addressing key issues affecting FEI members within the information and communications sectors.

The current debate over alleged dangers to health caused by mobile phones is sure to be one of the major areas of discussion.

Short has been in the electronics and telecoms business for 25 years including 12 years in cellular. He was chairman of the GSM Association between 1996 and 1997 and is chairman of the UK Mobile Data Association.

The debut of WiMax wireless communications next year could therefore pose a threat to the revenues of mobile phone giants.
Rob Bamforth principal analyst at Quocirca commented: "It´s certainly a move mobile operators need to take seriously. But I think the real challenge will be in how companies communicate their differences how 3G is different from WiMax and WiFi."
WiMax will enable users to log on at hotspot´ areas and make voice calls over the Internet using VoIP software from providers such as Skype without using a standard phone network.
Bamforth adds: "It´s not necessarily a bad thing for phone operators in the long term. I believe wireless operators will eventually move towards a subscription-based model of payment rather than paying by the second or the megabyte. The key for phone operators will be keeping up with these rapid changes in the wireless sector."
Pipex intends to roll out its wireless network to six or more cities by 2008 and aims to be present in 50 urban areas. Intel Capital the chip-maker´s venture capital investment arm is investing £14.5 million in the new company which will be called Pipex Wireless.
The announcement comes just days after Pipex acquired Homecall the fixed-line business of telecoms tycoon John Caudwell for £43million.
Pipex chairman Peter Dubens claimed the company would now have more than a million customers in the UK across broadband voice and hosting.

They include Little Britain The Office League of Gentlemen South Park Premier League Greatest Moments and Music Video Anthems.
ROK chairman Jonathan Kendrick said: "These six new titles will be available exclusively online before we release them into selected mobile phone shops over the next few weeks."
The titles cost £16.99 each. ROK Player memory cards are compatible with 18 handsets.

His unexpected departure is believed to be the result of a personal clash with boss Kyle Whitehill Vodafones director of enterprise business unit.
Vodafone refused to be drawn in to the details of his departure but a spokesman revealed: "He is leaving to pursue other career opportunities."
Sources familiar with the company admitted Huggett did not attend a 400-strong internal Vodafone sales conference that he was due to participate in at the Newbury head office a couple of weeks ago.
Huggetts exit follows a number of high-profile executive departures at Vodafone over the last year. A rift in the company is reported to have grown between the so-called "Newbury Boys" a group of executives led by Sir Christopher Gent who oversaw the firms rapid expansion in the 1980s and 1990s and other senior management figures including chief executive Arun Sarin.
In March this year Gent further fuelled rumours of boardroom politics by stepping down from his position as life president further severing ties with the company.
The loss of other key figures includes the ousting of marketing director Peter Bamford in March and the imminent retirement of deputy chief executive Sir Julian Horn-Smith in July both thought to be part of a wider boardroom strategy by CEO Arun Sarin.
Other notable departures include former finance director Ken Hydon senior manager for business partnerships Jason Rigby and head of dealer sales Iain Graham.
This latest departure is likely to cause further concern for the company which has undergone significant changes over the past year including the sale of Vodafone Japan for £8.3 billion in March and the return of Bill Morrow from Japan to head the networks operations in Europe.

This follows the news that Gnarls Barkley hit Crazy reached number one this month on the strength of digital downloads.
Planet Funk´s single Stop Me will be sold exclusively via downloads on 3 from May 8.
Band member Alex Neri said: "It makes perfect sense for us. People´s musical habits are changing and millions of people now effectively have a record shop in their pocket 24 hours a day."
Mobile downloads already account for four per cent of the singles chart and mobile networks claim more than 16 million music video sales or song downloads in the past two years.

Virgin Mobile users simply send a blank text to 22SOS (22767) and Virgin founder Richard Branson calls back within five minutes with a range of light-hearted messages you can use as your excuse to get you out of a bad date or meeting. If you already know you´ve got a tough situation coming up you can organise a specific time for him to call you.
The service is predicated on research by the network that found 76 per cent of women and 65 per cent of men wish their mobile would ring during a bad date or work meeting to let them escape.
Messages include a personal welcome to the mile-high club which notes that cameras have been fitted in aircraft toilets.