Can you connect an iphone 4 to a t-mobile company even though it us to have an at and t line?
I think you would have to discontinue one service so as to be able to use the other. You will have to contact the service provider you want to use so as to get the basics of the service. You can get activation with them after the inquiry.
My step-brother has an iPhone 4 on T-Mobile, but as far as I'm aware it only gets Edge service, not 3G. I could be wrong though, about the 3G, but it does work on T-Mobile.