Someone clamed me without my knowledge

[Anonymous]

you  haven't provided a lot of info,  in any case all you can do is paper file.

some pssibilities

1) you used IRS nonfiler website to get stimulus.  the IRS reagrds this as a 2019return filing

2) someone messed up in entering their SSN

3) could you be someone elses dependent

4) you could be a victim of identity theft

5) other.