Phone activation

I have bought a new Samsung A16 unlocked and have already called Amazon to confirm it's unlocked with ALL Carriers. While activating It, I get a message saying it's incompatible. This is a common problem it seems how can I make Xfinity add it to there data base and not run me in circles again. I know the phone works and is unlocked it just seems no one a Xfinity knows how to add it to the data base.