Non disclosure and Unfair treatment

Hi I had an account with Cell C for so many years and I decided to end my contract last year so I visited a cell C store who put me in contact with a call center agent, she canceled my contract and I did mention that the debit order has gone off already for the month and she assured me that that would be the last time they debit my account. To my surprise a few months later I was handed over to attorneys because I owe you a cell C money when I tried to explain that this account was canceled I was told that I was supposed to pay a cancelation fee of R250 which I was very confused because nobody told me about it.. However in December I paid the R250 into the cell C account because I was been called all the time and it was irritating. My problem is after paying the R250 I'm still been called by the attorneys everyday I am so frustrated I don't know what to do anymore... can you please assist me