Intermittent T-Mobile service on Iphone 4S
I just purchased at&t iphone 4S. At&t unlocked phone and I used I-Tunes to reset and update to 8.3(12F70). Installation on T-Mobile network was successful but soon service intermittently dropped on and off. I spoke to Apple who assumed problem was resolved when service came back. Apple told me that since this phone was so old, any other assistance would require payment. Powering on and off does not resolve problem. Locking and unlocking does not resolve problem. Any ideas?