Mtn black Friday deal was a ****

I took out a 50Gb deal, 30GB anytime + 20GB night express, this is apparently called my mtnchoice 10g at R299, From December I have been given different amounts of data, I called Mtn and went to the store where I took the contract and was told I will get the outstanding data and that I am not the only one complaining about this. I've been getting 10Gb less From December and this month its 20GB less. I have been paying the full amount every month and instead of Mtn giving me the balance of my data they are giving me less. This is unacceptable, I am going to cancel that **** black Friday special and not pay a cent as MTN owes me a lot of data. This is pathetic, actually its ***** as MTN deceived people with their **** specials.