I guess it should be possible o avoid the subscription by pressing on the empty screen area above the popup dialog (as everywhere in maemo5). Haven't tried it though... I have fallen into the trap too by just hitting the "Done" button.

In my opinion the dialog that asks about the subscription really should have "Yes, subscribe" and "No, don't subscribe" buttons instead just the "Done" button and not offering a clear way to refuse the service.

Regarding the error when unsubscribing: I noticed that when pressing th unsubscribe button it sends out the SMS but doesn't disable the button. Pressing it a second time, sends out a second SMS. A few seconds later you get get two replies. One containing the unsubscription confirmation, and a second one containing the error message because you are already unsubscribed. I noticed the successful unsubscribtion only at a closer look.

This clearly shouldn't be the way to go...