Should I take this further?

I cancelled my contract on the 7th of November 2020 for number ***. It was a data contract that included charges for a modem. The modem had to be returned 4 times because it was defective. Eventually we had a working modem but then still had no Internet as the sim card was now faulty. Since we rely on Internet access as teachers this was a major issue that resulted in disciplinary action against myself because I could not access my classes. We waited out the contract and cancelled as soon as we were able. Cell C then deducted a whopping R1012.14 from my account for a service I never received. Reference number *** led to a refund of R559.96 on the 9th of January. However, reference number *** and its escalation have yielded no results or feedback. As the one consultant would have me believe, this means we were charged R452.18 for services not delivered between 1 and 7 December. That is beyond unbelievable. In addition, since I have heard the same s**** each time I phone, the automated system informs me that I have 41.31GB available and my current usage is R48.72 However, I cannot use, and never could use this data since I am not permitted a new sim card as the account shows as cancelled due to non-payment. Cell C, I need you to fix this immediately and ensure that the credit record I pride myself on is not tarnished because someone clicked the wrong icon. I have now spent a total of 193 minutes to your call centres, never received any feedback other than a partial refund and despite providing me number for callbacks have now had to phone each time.