O2 still keeps charging on me 2 months after contract cancellation process has completed.

Hello.
It is not actually a question, but I expect to have a chance for communication with an O2 stuff in English and to let the problem resolved here.
As in the "Thema", I made an application for cancellation of my DSL contract in mid May and already got a cancellation (complete) letter in early June. (I absolutely needed the termination, cause I moved out from Germany permanently. My German is very bad, so I asked one of my German coworkers for the actual application (phone call).)
However, I received "rechnung" emails in June, July and August.

Here, I would simply ask for stopping further charge and to give my money back.
Thanks in advance
regards,

hibiarata