@Bettywang
If you can still login to your Public Mobile Self-Serve account then the account is still active. All you need to do is buy another Public Mobile SIM card (or eSIM, if the phone supports it), activate it, and install it in your phone - this will become your new Public Mobile SIM for your old Public Mobile phone number while your (lost) old Public Mobile SIM is permanently deactivated and useless.
If you can't login to your old Public Mobile account then it's gone. Terminated. Forever. Along with the phone number it had.
If you're bringing your phone number from another provider to Public Mobile then you need to request a Mobile Number Port. Do it from your new carrier (Public Mobile in this instance) instead of from your old carrier, this will ensure fewest delays and best odds of success. Keep using your existing (old carrier) SIM until it doesn't work, then install your activated (Public Mobile) SIM to keep using the same number with the new provider.
If you're bringing your phone number from Public Mobile to another carrier then it's the same process as the above paragraph. You still request the number port from your new carrier (with whatever support link or form they provide), not at your old carrier (Public Mobile, in this instance). You keep using your Public Mobile SIM until it doesn't work anymore, at which point you switch to your (new carrier) SIM. (If you don't have a valid Public Mobile SIM then see first and second paragraphs.)
