Cell C big ****

Cell C is a ****!!! I got a call from cell C consultant offering me a sim card data deal and I told the lady that all my numbers are busy and one of them is under cell C contact. The lady said if I take the deal all I need to do is to call cell C call center and tell them to port my new sim number to existing number and I did so. I was told that it's not possible to port new number to contract number(existing number that I'm using). I went to cell c store to return the new sim card and they refused to take it saying if want to cancel the contract I need to pay R2400. Now they disconnected my existing number which I pay every month