Being billed for calls I did not make

At the end of August I received a bill from Telkom which stated that I was being billed for 3 phone calls I did not make. There has never been and will never be a telephone plugged into the Telkom line. I use it purely for ADSL. In addition, the calls where placed while my line was faulty (12CRK210815). Since September 17 I have been asking for a resolution to these calls with the same useless response from Telkom: \We apologise for the delay