Is my Verizon iPhone 5c unlocked? I have a Verizon iPhone 5c. Is it unlocked so that I can just go to T-Mobile or AT&amp;T prepaid, by just popping in the SIM card?
If you bought the iPhone at full price ($549 or $649) then yes it is unlocked.

If you and bought it subsidised (where the price is $99 or $199), no it is not.

This restriction is required by the carrier, because they paid the remainder of the price, and will claim it back from you (with a tasty profit!) over the duration of your contract with them.