Not getting what i was told

I took out 2 contracts with mtn and the manager Blessing helped me. One was an anytime 100 contract and the other one an anytime top up 100. On the anytime 100 he said i would get 500megs of data per month and the top up i would get 150 meg. Now it seems i am only getting 150 meg on the anytime 100 and on the top up i get nothing. A verbal agreement is as good as paper and i have witnesses that was with me hearing what he promised me. If this does not get sorted they can take both these contracts and shove it as blessing is not to be trusted and he does not seem to care because he has already recieved my sales.