Pixel 8a, renewed, supposedly unlocked, need some help!

Hello all - looking for some help with a new line.

Bought a pixel 8a, renewed, from amazon. upon receipt, turned it on and signed in with a google account. Phone tried to point me to ATT to setup cell service.

Checked the IMEI number and it revealed that the phone was not unlocked (despite product description at Amazon). So, I unlocked it through the ATT tool and got a confirmation that it worked.

Tried with visible again, still no luck. Error message stated that the IMEI was not available.

Spoke with visible chat, got a real person, and the person checked. They told me that the phone was unlocked but that it was only going to work with ATT.

It was my understanding that the pixel 8a, once unlocked, should be compatible with any network. I'm not concerned about the money, I can do the return and get full refund. I just want to know that if I go to bestbuy tomorrow and buy an unlocked pixel 8a, will it work?!?

Any tips or insight? Thank you.