How do you deal with a network provider on the wrong?

In November I upgraded my phone contract and opened a second one, they delivered one phone. I called and was told my second contract was cancelled and there was no reason. I re-opened the phone contract and opened a sim contract as well. They only delivered the sim, I told them I don't need the sim anymore and cancelled it. The phone was delivered late November after I already called and canceled my sim contract since I'm not satisfied with their customer service. My phone contracts each are R328.99, the sim was going to cost R200, but was cancelled. On the 20/12/21 they charged my account R671,31, and again on the 21/12/2021 they charged R328,99. I called they couldn't explain clearly why, I reversed the R328,99, they called explaining the first debit order was for the sim and cancelling fees of some sort. I let it go and transferred R328,99 via EFT(which to this day has not been located, hence I have been on arrears ever since). CellC keeps making unscheduled debit orders after actual debit date, sometimes 2 or 3 times a month, which sometimes bounce and I have to pay the penalty fee both at CellC and at my bank. I have lost all hope trying to fix my account and no one at CellC is willing to help. I have about 6 Reference numbers from all the calls I keep making trying to fix my account. The arrears keep going up every month while CellC is the one who actually owes me.