Bad Customer Service and Reneging on an Offer

I took up a premium subscription with Dstv on the 24th of November 2018. The consultant assisting me advised me I can get premium for R699 if I do not downgrade. The price would be about 3 months if I remember correctly then after I pay the full premium price. I agreed and asked how much I need to pay then and was advised R728 after he made his calculations. I have since logged into my self service and noticed I had R894 due for 25 December 2018. This obviously meant no R699 package was added. I called your customer service and spoke to Hlengiwe who told me they need to listen to call and get back to me. That never happened. I called today and spoke to Duncan who said he is a team leader. He was very arrogant and dismissive. He told me he is busy he will assist tomorrow. I asked to speak to his manager. He told me his manager is also busy but will call me by 16:00. That call back never came. I spoke to Thobile after 18:00. She also did not do anything to help and I am still in the same position I was in. All I keep getting told is I will be called back and the call backs never come. Why offer me something then turn back and change without informing me? Why are you refusing for me to listen to the call? Why are you refusing to honor what your consultant offered me?