Data nightmare

I am so fed up with Vodacom I went over to mtn because of this but my mother is still with them and when I wanted to cancel her contract to also migrate her to mtn Vodacom made her promises to match their deals so she upgraded with Vodacom again.... Big mistake they promised her 5 gig every month but now she only gets 500m and I have to call in every month to rectify this then speak to 3 different people making a lot of promises to fix this but it just doesn't seem toe happen I have asked them to listen to the original recording but that doesn't seem to happen as well why record it then. Just fix the problem why is it so difficult for Vodacom to keep to their end of their deals.