My stepson's iPhone 6 won't make, or accept, calls. He has replaced it with a new iPhone 7, but this has got me really curious as to how or why this would happen. I don't know any more about what the symptoms are, but does this make sense? Internet connectivity is fine, and calls over IP works. Part of me is suspicious of the store he took it to (not an AT&T store but and authorized agent.) Apparently it was a problem with the SIM card connection (he is using the same SIM card on his new phone, plus a second AT&T store (a real one) swapped SIM cards and it didn't matter.) Any thoughts? Would this be repairable? Would it be worth repairing to sell it, perhaps, or keep as an emergency backup phone?