Of course Verizon can't find the phone on their system as it's not from Verizon but from ATT and is UNLOCKED. Can't Verizon just give the current customer a nano sim card and activate it? Other carriers do.
AT&T iPhone 5 is not compatible with Verizon. It does not have the CDMA capabilities needed. It is not a matter of being locked or not locked, it is just not technically compatible with the different network.
The GSM ATT phone won't play well with CDMA Verizon networks. Verizon will most likely say no. Unlocked just means it isn't locked to 1 network/carrier. It does not however mean that it can be used anywhere on any network. the technologies still have to match.
What phone did you give your friend? Almost all non-Verizon phones cannot be used on Verizon because they lack CDMA capabilities. There are a select few (such as the iPhone 6 or 6 Plus) which if you put an already active SIM in the phone it will function but with limitations. It will always show up as unrecognized device on My Verizon, and it will not be eligible for out of contract reduced monthly pricing.
Iphone 5
