Mtn failure

Over the black friday weekend, Mtn ran a promotion on contract deals that advertised that for R299 per month you will get the following:150 minutes, 100sms, and 14Gig data bundle over 12 moths. For the past three months i kept my part of the agreement. Mtn is yet to do the same. I have repeatedly been to the outlet (Mtn Westgate next to Clicks) where i signed up, to lodge my complaint and i got a promise that my complaint will be escalated.I ended up talking with the branch manager and he made some calls to his head office and i was promised again that the 14Gig data will be released in about 24 to 48 hours time. I am still waiting. Mtn recently sent me a message that as of 1st of March2019, they will have to put my internet on hold. I now am put between a rock and a hard place, i have been paying three months now for a service that mtn has not been able deliver and now face a possibility of having my internet suspended because my data is "depleted". Where does one begin to fight gigantic establishments such as this. On one hand i am expected to pay religiously the R299 per month as per contract. If i decide to stop, i may be blacklisted. i strongly believe in our laws as a country that they have at heart consumer protection rights embedded in them. But from here where does one go? I am deeply concerned.