Accidentally logged my student id with the wrong account; how to unlink?

long story short: used to live in the US and went back to my homecountry. i accidentally used my student id verification on my US account (and ofc it didn't worked), so when i tried it on my new account, it says that the id had already been used on another account...

so, how to unlink my student id from my old account? thanks in advance!

(i use an android device)