I have tried to research whether or not you can successfully take a used iPhone 7 from an AT&T account and use on the Verizon system? We want to replace our daughters current iPhone 6 (paid off on Verizon) with an iPhone 7 from a family member that was purchased (and paid off) on AT&T to our Verizon account. Can you tell me if this works? Our family member was told that the phone could move to any network without issues when purchased but in reading it seems like that might not be the case?