How to know if my phone is carrier locked
There are a few ways to check if your phone is carrier locked or tied to one carrier. First, you can try inserting a SIM card from a new provider. If the phone doesn’t connect to that network or you receive a message that reads “SIM not supported,” then you can assume that it’s carrier-locked.
iPhone users can go to Settings > General > About and scroll down to “Carrier Lock" or “Network Lock,” which will indicate that there are no SIM restrictions if your phone is unlocked.
Android users can check for a similar message under “Network” or “Mobile Networks.”
If you’re unable to determine if your phone is carrier locked you can contact your current provider to clarify your status and even unlock your device if it's eligible.