It’s a shame you didn’t get this resolved on day one. Take it to Apple.

If your return period has lapsed they won’t refund you but they will probably allow you to exchange it against an equivalent M3 machine. Talk to a specialist in store and they can ask a manager. Can’t guarantee this’ll work but so long as it’s an exchange as opposed to a refund they may well make an exception. That’s assuming we even get an update to the MBP line. I think the iMac is a much more likely candidate for an M3 update but who knows.