MTN not giving me my full allocation of minutes and data as promised for my sim only upgrade.

I was contacted by someone who identified themselves as someone who is calling from MTN regarding upgrading my contract. I accepted the sim only deal. After the first month I noticed that I had not received all of my allocation of minutes and data that was promised to me as part of the deal. I thought that perhaps it was a pro rata thing and I waited for the next cycle and I noticed that again there was a shortfall on both minutes and data. I contacted MTN many times and I was transferred to many people and even a 3rd party company who I had never heard of. Eventually I received a reference number *** on 19 September. After almost 2 weeks I called to ask them regarding the reference but I was told that there was still no answer. I do not understand what investigation takes more than 2 weeks. I am not getting the correct allocation. I would imagine they need to play back the conversation when I accepted the deal and realize that there is a mistake on their side and they need to rectify the mistake. I have been an MTN customer for many years now and after this experience I feel disappointed and I really don't want to talk to another consultant I just want the issue resolved so I can move on with my life.