Can parents still claim me as a dependent if I filed my taxes before them. put that I can be claimed by someone else. They're making a fuss over it saying cant claim me?

How old are you?  Were you a full time student in 2019?

Yes - your parents can still claim you as a dependent.  However, since you filed your return first, the IRS computer just sees that your SSN has already been used on a return and won't accept other returns with your SSN.

Your parents will have to mail in their return.