After you file

I filed my taxes in Early February before the American Rescue Plan Act was passed and I was billed for $330 because I received unemployment and did not withhold federal taxes from it. There is no way that I would owe for any other reason, as I made only about $19,000 in 2020 without the $6,500 of unemployment I received! I got a bill in the mail the other day for said $330! What do I do with this bill? And do I file an amended return, or do I just wait for the IRS to automatically correct my 2020 federal return for the ARPA changes?