OVERCHARGED!!!!!!

I'm currently on a contract and have been paying R488 for the past 12month and on my surprise R653 was deduct from my account,I called customer service and a lady name Sinazo Mguqulwa was not giving me straight answer to why I am deducted so much instead on my monthly premium,she kept on going back and forth to her team leader to ask questions,but wht strike my attention was when she said I was over charged because I had to pay for a decoder,my question to her was why wait 12 months to deduct the money for decoder will I pay for the cable and the satellite too? I took th contract that include everything and free installation.can I please be assisted urgently have been a loyal customer for years I believe I deserve a good customer service Sinazo promised to call me back with more information to why I was over charged...till today I'm waiting for her call,why put people who don't know what they are doing in a very crucial department.DSTV never sent to response to a mail I sent too I need my money refunded to my bank account