Worst cell service

I upgraded my MTN data contract in april. I was told that I would pay R299 a month and will receive 40gb+40gb a month. I have only been receiving 20gb+20gb. I have phoned in about 7 times each time receiving a ref number each time but nothing ever gets done. Last month I requested that a supervisor must get involved to fix my contract. Twice I was told that a supervisor will call me back with 3-5 working days. 3 weeks later and still no call back. This is the worst service available and considering that the contract I agreed to was for 40gb+40gb and only receiving 20gb+20gb for the same amount of money is what I consider *****. MTN is *****ing my money by not giving the proper amount of data. Dont trust MTN.