Sorry, you can’t buy a $580 iPhone 5 from T-Mobile and then sign up with another carrier — you have to give T-Mo at least once month of service.
T-Mobile is still selling a commitment-free iPhone for full price even if it doesn’t stand to gain from the transaction as a service provider. T-Mobile is essentially becoming a phone retailer as well as carrier, and I think that has significant implications for the industry.

I am using T-Mobile! T-Mobile Helper is try to convince other peoplle to use T-Mobile!