On the Dashboard go to System then Accounts. In there you should see an option for your memberships. Go there and turn off auto renew for the trial.
If that fails then you should give support a call and have them turn it off for you.
Did this solve your problem?
Sorry this didn't help.
Great! Thanks for marking this as the answer.
How satisfied are you with this reply?
Thanks for your feedback, it helps us improve the site.
How satisfied are you with this response?
Thanks for your feedback.