Signed up for amazon prime trial, lost access to the account/email.

Signed up to amazon prime trial on computer, forgot the email used cos it was all done on keychain and thus saved on my computer account. But I gave the computer to a relative when I got a new one a few days ago, and without asking me my relative completely deleted my account from the computer, so now I can't remember the email used to even try and recover the password. Any suggestions on what to do before I'm charged? Contact the bank? I tried calling amazon but I didn't get through to anyone.