Is it too late to reverse what I put on my w4?

Im a moron and filled out my w4 incorrectly. I claimed too many exemptions. I put “2” instead of “1”. Im single, no kids, its just me.
NOW, I did my taxes myself and have to PAY. Ive never had to pay before. I thought maybe there was an error on my w2 so I went back to my employer and we did some research and it came back to that I filled out the w4 wrong. DARNIT!!
If I was to go to an actual “tax company” and have my taxes done by them, would they be able to correct my mistake for last years taxes, or am I basicly screwed and have to pay $500.
I hope this made sense.