“Free” NOT free with Vodacom

I qualified for an upgraded to a new package about 2 years ago. When I upgraded, I was offered a special where I get another phone and SIM card (with R100 airtime) every month in addition to my contract which gets upgraded. I was assured that there would be no extra charge for the phone and that I will only start paying for the phone after the 2 year contract came to an end. From last month (which is 21 months after the contract was taken up) Vodacom started charging me R100 extra each month for the extra “Free” phone ad SIM which I got 21 months ago. Along with this extra charge, my discount which I had on my primary contract for the 21 months was also discontinued! I have contacted their customer care line numerous times, obtained numerous reference numbers but no-one can help me. Every month they just continue to over charge me again and again. Never take up any “Free” or “Discounted” products from Vodacom, they will keep if free or discounted for the first few months, but after that they will start charging you for it.