NOS assistance needed

 I find it really odd that one has to join a NOS forum in order to complain in writing, as opposed to telephonically, about a NOS problem.

In brief, on May 15 I cancelled my NOS contract (C********), in person at their offices in Albufeira. Despite a written confirmation of the cancellation, NOS is still cashing the debit order. 

I would obviously like this to stop immediately and my account to be refunded