I have my new unlocked iPhone 6, unlocked I ordered from Apple, no contract T Mobil phone. I have activated it using my SIM from my now retired 5s on the ATT network. I think, not totally certain, that my network voice reception is not as good as when I use the iPhone 5s. Since the Verizon iPhone 6 is unlocked for GSM networks, is there any difference in a T Mobile iPhone compared to a Verizon iPhone on the GSM networks? I realize the T Mobile phone won't work on a CDMA network. But on the GSM networks there any difference in the phones from different carriers? Thanks for any insight the group may be able to offer.