Poor Service

Cell C probably the worst mobile network there is. I settled my account by paying a huge settlement fee. Their manager quoted me an amount and when I asked if that was the final amount he still confirmed that the amount given is for all outstanding debt. Once paid I thought that I was done with the contract but to my surprise I still owe an amount. I called them 6 days ago and was promised that will be rectified and it has not been done. I need to do a sim swap and cannot do it due to their poor service. What's worse is when you try to explain your enquiry they treat you as if you stupid. The reference number I received was ***. It will probably take another week for someone to call me.