Old man disgusted by Multichoice overcharging him despite a price lock

I am and 87 year old man who signed up for the price lock amount of R759/month a few months ago, and have been overcharged ever since then. I have since made numerous phonecalls, sent multiple emails and been to the offices of multichoice more than once. I have been advised that I will be credited for the overcharge, and months later, they continue to take advantage. How long does an old man have to wait before getting credited with money that is owed to him? As a remaining DSTV customer of many years, if there was another alternative for satellite TV I would have cancelled my subscription. Disgusting service levels to say the least.