Telkom must check when last I used their data, I don't owe you and work on customer service

I went to telkom to have them Cancel my contract due to very poor connectivity for good 2 months straight there was no network. On the 15 of May I went to east rand mall for enquiries I was told there is nothing they can do since I moved to a new place thats why there is no network. Right there and then I requested for immediate cancelation and I was told I will forfeit my data for May which what happened, end of May my account was debited 779 rands. The only thing given to me was a reference number and was told that is my proof of cancelation. The staff at East rand mall has poor customer service and bad attitude.