Cell C refused to pay back money owed

We ( My fiance and I ) have had a Fibre contract with Cell see from about 2014, which is all good and we made our monthly payment every month without ever questioning it, however now after 6 pr so years by chance we noticed on our statement that there has been R80 going of for a sim card. When we questioned it, they realized that it was a sim that was supposed to be cancelled automatically in 2014 once our fibre line was active, however they never cancelled it and it has just been deducting R80 every month since 2014, which brings the total to about R6000. We then requested them to cancel it immediately and to refund the amount that the took from us. We dealt with a lady called Stella, who then informed us that the refund was approved however they refuse to pay us out the money and says they will credit us and that it will then go towards our monthly Fibre costs, however we were planning on canceling our line with Cell C and move to another service provider, and now we will have to stay with them for another 5 or so months just because they refuse to pay us back the money that they took from us. This is ridiculous seeing as how they took the money and now just want to give us a credit when we do not want a credit, we want the money back, and most probably they will forget about the credit and still debit our account. All of this after I gave Stella such a great review when initially signing up with Cell C, and now that there are issues like this she just says we will get credit.

I really do not think that a company as big as Cell C cannot refund a loyal customer R6000 that they took from us because of their *********** staff that did not cancel a sim card all the way back in 2014.