you can however if its not unlocked from the prior owner you’ll be stuck with a phone you cant unlock down the road since technically youre not the original owner. make absolute sure its been unlocked.

Oh, yeah, I can see how being stuck with someone else’s data would not work.  How would I make sure it’s really unlocked?  There are several from mobile phone dealers that say TMobile Unlocked, so I would assume that is correct, but now I’m skeptical.

If you don't mind buying used try going to Swappa, the phones that are sold on the site are certified to be unlocked and not blacklisted.

At one time you had to have a SIM from a different carrier to test in the phone but my current phone has a SIM-lock status in the Settings menu. In my phone it’s under About Device.