Poor enquiry follow up

When I took out a contract they did not explain to me that it was an open line. They debited amounts way over a R1000 whereas the contract was only for R110. I logged an enquiry as well as tell them to cap my line in December but to date they still did not do as requested. For the month of February an amount of more than R2100 was debited and still no response from them. I have other debits that needs to be payed with the money that was overcharged by them. If this affects my credit record negatively then I will surely take this matter further.