If you send them an email demanding your account be canceled, CC companies will usually let you use that to dispute further charges until your account is actually canceled.
They enabled auto-renewal on a domain name I have there that didn't used to have it, and want me to call a US number (i'm not in the US, i'm not paying international charges) to cancel auto renewal.
I also requested they close and delete my entire account with them.
By using something like the aforementioned service, at least you can prove without a doubt that the message was sent at a specific time, putting the impetus on the receiving party.
(Not suggesting they do this... but if they think you owe them money, they certainly could)