No authority to debit my account

I am rather upset as I signed up for the Price Lock option and consequently gave DSTV permission to debit my account (via debit order) for the agreed price lock monthly subscription. This is for R959 per month. Then they decide to debit my account for R2030.13 on 2 Oct. Needless to say I was furious when I saw this! I called the contact centre who said their systems are slow and they could not assist. I logged in online and none of the transactions make sense to me as the descriptions are all jargon I do not understand. I then logged this on Facebook and finally got a response saying that R1127 was debited for the "payment plan" and R903.13 was debited for the residential account. Who authorised DSTV to collect money off my bank account for my existing residential account??? I did not even have a debit order on this account??? And what does this have to do with my new "payment plan" agreement? Why would I pay two premium subscriptions for the same month? Why did they not cancel the "residential account" when the "payment plan" was activated? This is not the agreement I signed and I am very upset. Your premium subscribers are shrinking on a monthly basis, and if you want to add me to that list, then you must ignore this complaint. I want my money BACK! You were authorised to only debit me for the agreed price lock deal. Nothing else. So please urgently refund me R903.13 - as quickly as you took it (no I am not interested in leaving the "credit" with you - give it back to me at once). Also - since you charged me a pro rata amount for September from the time the decoder was delivered, and yet I already paid the premium subscription for the whole of September, I need a credit on that too. Then make sure this does not happen again, or I will cancel the whole deal as you have not upheld your side of the agreement, and chose to add additional costs to my debit order that had no relevance to the agreement I signed. I will also report this to the Payments Association of South Africa as you are abusing the mandate I gave you. At this stage I will not instruct my bank to return the debit and put a stop payment, (which is the obvious solution) in order to allow you the time to rectify this. Thank you.