Enquire about wrongfull deductions

I received my itemised billing for March where it reflected that there was 2 calls made. The 1st call was made at 11:33am and lasted for 1:59. Then another call was made to the same number at 11:34am same day and this call also lasted 1:59. I logged a service request asking Vodacom to investigate how this can be possible to make 2 phone calls a minute apart but have a conversation of 2 hours. Two weeks later I have not heard anything so I called again and was told that the service request was closed. The call centre agent then opened another service request. I received a sms with the service request number. Again two weeks when by with no feedback. I then phone again to find out what is happening on the service request. Once again I was told that the service request was closed by the technical department without any resolution. The third time a service request was logged. The call centre agent promised me that she will follow up with the technical department and phone me the following day. Again no phone call back from the team leader. Today I phoned again to do a follow up with Lerato just to find out that she is not working today after I was promised she will sort it out.