I want to use my teen daughter's iPhone 5c as a "starter" phone for my younger daughter. Will the 5c work with AT&T or StraightTalk?
Is there a reason why you don't want to activate it on Verizon Wireless on either a postpaid or a prepaid account?
Verizon will no longer activate 5c
That's likely because it isn't capable of HD Voice or VoLTE. The phone itself should be SIM unlocked, but you might not get LTE on the other carrier.