Account and payment issues with Cell C

Hi, my name is Ansie Pieters, cell nr ***. I am using my friend's hellopeter account. I have been struggling for 3 months to sort out my account with Cell C. In May, they debited R3555 from my account which was correct, but in July they debited both 3202 + 3555. Which means they took 3555 twice from me. I did make contact and I did sent through all the proof, but up and till today they only log reference numbers, but with no contact or solution. As they took the 3555 payment twice, I did not make a payment seeing that there was a credit on my account so I didn't bother to pay money to the account. Once again this month my account shows a back log plus the amount due for August. I am desperate to solve this issue, but can't seem to get any reaction or assistance from Cell C.