Do the right thing Cell C

In nut shell contract finished Cell C still took money off, I kept reversing it. They changing info on my security check. They even changing the payment reference no which.is apparently *******. This all started middle of last year it has now affected my credit rating. No one can seem to help me. After researching it is happening others. Can Cell C do.the right thing and call me and short it out surely it cant be that difficult