MTN Contract ****s

I don’t know how many times I have had a back and forth with MTN to cancel a cellphone contract. The contract ended and I even paid the cancelling fee as they requested but now I keep getting these bills I am not even sure what they are for. First it was R400+ and they told me the person who was handling the contract didn’t make it immediate as they had communicated and I had to be changed that R400. There is always one cost after the other and always because someone internally didn’t do one or two but not the customer suffers with the payments. I need help honestly.