How do I receive a copy of my final bill?

How do I receive a copy of my final bill? I just finished my service with AT&T and switched to T-mobile. I elected to be paper-free so I would only ever get my bill in an E-mail. Now that I have switched my phone to T-mobile though, I can't log in to my account and I haven't received the Bill like I should have. I better not get some collectors agency calling me. I need to pay this bill so I need to receive a copy of it. Can you help me with this.