Billing error

I have an issue I normal pay R519.00 however this month was billed extra with close to R150+ when I called the call centre was told that its a billing error even today am still sitting without any resolution what a pathetic service they have. I mean I took price lock for a reason and no one has the nerve to contact me and give me feedback. I went through my bank statements to even check if I have any unpaid debit from multichoice I have none. Their service is just very poor and I regret even taking 24 months deal with them....