Trying to close account but locked out

I have been trying to close my seller account but I was locked out. The fees had got too high and everything else so I figured I’d just keep it active incase I ever wanted to go back. I just received an email from one of the brands I was selling asking for proof that it’s authentic but I can’t log into seller central now to reply or close the account. I also haven’t been able to contact support since you need to log in to request a call. Does anyone know what I can do?