Vodacom in-ability to execute closure of an account.

I have left South Africa November last year. In June I requested to close my account, I received an invoice of the outstanding amount plus documents to sign etc which I oblidged to and forwarded proof of payment as well as all the documents dufully signed etc. We are in November and they are still deducting monthly instalments from me how is this possible? All enquiries return with a request with additional information to verify my account "as it is important to VODACOM" I believe it has more to do with me contributing to their well-being?