NEW YORK ( TheStreet ) - Wireless company earnings season is revealing that some of are having trouble keeping customers satisfied -- or even keeping customers. This country's number four major provider, T-Mobile USA, just reported in its fourth-quarter financials that, despite some signs of growth in its prepaid customer rolls, they continue to lose contract customers. The bottom line: a revenue decline of $1 billion for the year, leading to an overall operating loss of $6.4 billion. That's up from a $4.3 billion setback in the previous year. It remains to be seen whether T-Mobile's upcoming merger with MetroPCS ( PCS ) will solve that problem, with that pairing set to be completed next month. Meanwhile Leap Wireless International ( LEAP ) and its pre-paid cellular operation Cricket lost more than 600,000 subscribers last year, which has left the company with a surprisingly large backlog of Apple ( AAPL ) iPhones.