Cell c wrong debit amount for the past 6 months

Ive been pjonjng cell c back and forth now for 6months. I was initially paying about R135 a month for my data sim contract. In august 2019 it all of a sudden jumped straight to R306 a month. I phoned them immediately to tell them they had debited the wrong amount so the consultant said they will open a case and they will get back to me in 2 working days then they diditnt. I phoned again the following month then they said they will escalate the case. This has been happening every single month for the past 6months and they still havnt sorted it out ive still been debited the R306 nothing has changed!!!!!