How can I be sure my phone is unlocked?

Episode 1081 (1:27:07)

Paris from Illinois
Apple iPhone 5

Paris has an iPhone 5 and he wants to unlock it. Leo says that on Sprint/Verizon, the iPhone is a CDMA phone. But if he unlocks it, he can buy a SIM card from AT&T or T-Mobile and it should work.

Paris said they will only unlock it for international calls. Leo says what they probably mean is that they unlocked the GSM slot and kept the CDMA side locked so the user wouldn't go to Verizon. But the SIM means he can go to either T-Mobile or AT&T and it should work. Leo advises finding a friend who uses T-Mobile and slip their SIM in to see if it works. Or, go to T-Mobile's store and ask them to see if it will work.