Cell C deduction more than agreement contract..

Unfortunately I had to put a 1 star review, to be able to write a review.. It would have been none if you ask me.. I am a customer from Cell C for more that 10 years now.. I currently have a fibre and 2 cellphone contacts with Cell C.. On this day 3 weeks ago I went through my monthly payments regarding the Fibre contract and saw that Cell C deducted R999 from my bank account every month and the agreement amount was R856 per month. I wrote a email to the Fibre department at Cell C and was answered a week later just to tell me that they don't have the 2018 contacts anymore and as far as he /she can remember the 10/5 meg line was always R999.. I rep**** to them with proof of a email I still had on my phone email account.. Since today not even a call or email to tell me they are busy looking at my enquiry.. Going on 2 years deducting money they shouldn't have.. But the worst of all is the silence.. And yes I have called them numerous times to get assistance, but to no avail..