Overcharged on my device contract

I receive a monthly rebate from FNB for the cell c charge that is incorrectly debited for my FNB/Cell C device.<br> The Cell C debit increased from R100 to R110 in Febuary but the rebate did not. <br> <br> I raised this issue at the beginning of May and nothing has been done. I have completed debit order dispute forms but the Cell C amount continues to come off my account ever month.<br> <br> I haven't received any response despite sending numerous follow up email. Thank fully my contract end this month but I would really like the soon to be R60 that i have overpaid.<br> <br> These are the reference numbers that i have recieved SD*** SD***.