i need help with icloud please

I bought a new iphone iphone 11 pro max i signed in with my icloud everythink was very good, after 2 days i want to do restore from my laptop,but i did mistakenly retrieved another backup .. because i work at a phone repair center and there are also backup copies for costomers,

Now there is icloud for someone i don t know him and i connot delete it , currently the account is requested to be confirmed with a password,

what can i do im very annoyed.. please if someone can help me