I have already sent a letter to O2 GmbH ( address: Telefonica O2 Germany GmbH & Co. OHG Kundenbetreuung 90345 Nürnberg) with my details and my new city registration certificate but did not receive any reply nor did they cancel my contract. The O2 filiale in my current city told me about this procedure.
I have been paying for past three months unnecessarily and would like to know about the solution. Please reply. thanking you in advance.