Getting bills for Cancelled DSL-contract

Hi O2 Team.

I had cancelled my DSL-contract since I have moved out of Germany from July 30th 2017. But still I am getting the bills for last 2 months. the amount is getting deducted automatically from bank account. 
I had sent the cancellation fax already ref number : 01805880088 with the neceassy proof documents.
Also I had sent the router back via Post.

Please refund the amount taken for last month.

 

KUNDENNUMMER: DE16277004
RUFNUMMER: 062143668332

Best regards 
Ananth Antony