Unclear communication and false promises

Good day

Towards the end of September I received a call from a multi choice sales agent, offering me a Dstv subscription (premium package including the explorer decoder) price locked at R749 a month for 2 years, I agreed to the deal and delivery was arranged.

10 October I had the decoder installed and set up, a few weeks later I receive a message from multi choice saying I owe R2200, I gave them a call to find out what this amount was for, I was told that I have 2 decoders, I explained to the person on the phone that I only have one and since I was already on the premium package before the explora deal, I had no reason to be using 2 decoders, the person promised to escalate the matter, a day after I received a message from multi choice saying I owe them R1400, again I called to find out what this amount is for, this time the person that took my call agreed that I should have been debited for one subscription and also promised to escalate the matter, last week Saturday 27 October I gave multi choice a call again to explain my situation, the lady that took my call insisted I had 2 subscriptions, so I was charged for connection and all that (mind you part of the deal was that installation is also included for free) so I explained that to her, she then said I had to advise them to cancel the other decoder/subscription, my question was that how is it that now that I took the price lock offer I am suddenly using 2 decoders, she promised to listen to the recordings and revert, till this day I have not heard from multi choice.

So what I want to happen is that multi choice either debits me the R749 or the R849 as normal, and refund me the difference of the R2200 they took from my account.