I did a direct payment to the IRS by mistake, I didn't owe anything but I thought I did. How can I get it back? It's been two weeks now.

what year? 2024 the IRS will probably refund it. How long this will take is unknown. 

you can contact the IRS

Call 800-829-1040
1) Choose your language,
2) Then choose option 2
3) Then 1
4) Then 3
5) Then 2
6) When it asks you to enter your SSN or EIN do nothing – wait - - After it asks twice, you will get another menu
7) Then 2
😎 Then 3

It should then transfer you to an agent. Note when its phone line are busy you may be on hold for a long while or disconnected

Thank you, yes for 2024. I will give them a call