INCORRECT BILLING - NEED TO BE REFUNDED

I signed up for an internet 5 promo at the end of November, the deal is for 5GB anytime data and then you receive 15GB night time surfer. The total for the deal is supposed to be R199 per month and the contract is for 24 months. December I was charged R1086.00 and now for January R905.00. I've tried getting feedback via the call centre, first time I received a case number (***1)saying that someone will call me within 48 hours, that was on 5 January. After being on the line once again with a call centre operator, the only answer I was given after being on the line for almost an hour is that the case is still being investigated. I would like this to be sorted out and to be billed the correct amount and also to be refunded for the obscene amount that has been deducted via debit order. It is ridiculous. I have never had any issues with Telkom / 8ta but this poor service will ensure that I will cancel all my contracts once it has expired.