Exactly how do I set up an unsubscribe page for the membership plugin?

I am using the membership plugin.

I thought I had set up an unsubscribe page using the [accountform] shortcode but it is not working and I keep getting e-mails from members who thought they were unsubscribing yet were rebilled.

I am using the 2Checkout gateway with recurring billing.

Please tell me how to set up the page and if I need to do anything on the 2Checkout end.