Cell C unable to solve SIM problem

I have various contracts with Cell C and generally very happy. However, on a DATA contract, I have had only troubles over the last month. The SIM just stopped working and in spite of telling me that nothing is wrong on the system, the SIM was replaced on the 17th of October. This SIM also did not work. On the 28th of October, I took it back to Cell C Cape Gate where the SIM was tested and found that it is not working. Once again I was told that according to the system noting is wrong and once again I was issued a new SIM. On the 30th I phoned Cell C Customer service and the technical department to me to go to another shop and get a new SIM. Once again they said that nothing is wrong on the system but maybe the SIM cards at Cape Gate is a bad batch. This morning I went to Cell C Soneike. Again they tested the card, and once again found it to be faulty. When they issued me a new SIM card I refused to pay for a replacement for a faulty card and the refused to assist me. Once again I phoned Cell C customer service who now says that they will log the issue and that someone will get back to me. For a long period now I was unable to use the DATA that was paid for and no solution is in sight and I am expected to pay for replacement SIM cards to replace faulty cards.