Can I used an unlocked AT&T iPhone 4s with a Verizon sim card?

Can I used an unlocked AT&T iPhone 4s with a Verizon sim card?

No, you can't. AT&T iPhone is GSM while Verizon is CDMA and they're incompatible.

You can use the phone on other GSM carriers like T-Mobile, StraightTalk, H2O Wireless, metroPCS, Cricket, Family Mobile, etc.

You can't use the phone on CDMA carriers like Verizon, Sprint, Boost, Virgin, US Cellular, C-Spire, etc.