accounts query - no response

we have a billing problem - TELKOM MOBILE billed our account for an extra handset that we never received they also can no give s proof that we received this. since August 2014 the have billed our account - in total fro three months. I decided to pay the contract balance which I should be paying every month and close the account - we have since ported to another network, but still keep on getting threats that we are going to be black listed and handed over and account that has now accumulated to over a R 1300.00. NOBODY of Telkom mobile responds to any e-mails or calls.. we have been at the branch - they refer to the accounts - the account refers us to the branch....