Cannot access account to end plan

Hello, 

I have been a customer for over 1,5 years and used to live in the US but moved out in April, I kept my phone number but recently decided that I want to end the plan. 

When trying to log in to do this, I am in no way able to access my account - my email doesn't work, my password doesn't work, not even my phone number works, and still I am being billed by VESTA AT&T P each month. How is this even possible? Do I track this through my bank somehow?

Please advise!