Your system error should not affect me!!!!!

Recently re-connected my dstv package after a year and paid R510 as you requested. Dstv Compact only costs R365 a month with the R85 access fee that comes to a total of R450 due. Now you state that I owe you R927.10. How on earth is this remotely possible? I have lodged about three complaints on your website and to date I have only received a simple mail stating that there seems to be a system error... No phone call? Do I as a customer really mean that little to you that you cannot give me a call to state that you are working on the issue? I am extremely disappointed in you guys REALLY! You seem to treat your customers unfairly as you know that you are the monopoly and that somehow gives you the right.... Words do not seem to be enough to express my sadness at this present moment... YOU GUYS SUC****!