Mystery Caller has tickets, and wants to make sure his phone works when there. Will the prices be high, and can the networks reduce the cost of traveling?

Mystery Caller can’t get a SIM-free Android phone to work. Sky emails won’t sync and, having downloaded a tune, how does he personalise the ringtone?

Mystery Caller is buying his 16-year-old brother a handset. He will spend up to £100 on one that will appeal to the age group. He also wants control to be put on internet access

Mystery Caller has a history of being clumsy by having his phone lost and stolen and wants to find out what insurance policies the networks can offer

Mystery Caller is after a phone with a good camera that can upload his pictures to social networking sites with minimum fuss. His budget is £30 a month

Mystery Caller is looking for a device that can run Sat Nav mapping and replace a standalone in-car unit. What could the networks offer?

Mystery Caller has landed himself a job in the city but the wrong handset. He’ll need one that offers push email. But his budget is £30 a month. What can the networks come up with?

Mystery Caller has read that EU rules covering web use on phones will be enforced to stop us overspending. Will the networks’ knowledge be up to scratch?

Mystery Caller is overspending every month. He’s on prepay topping up by £40 a month and wants to tighten his belt. How would the networks save him money?

Mystery Caller needs mobile broadband, but studying in the city and living in the country means coverage must be fantastic. Can the networks deliver?