Data bundles disappear

The way Vodacom data gets depleted so quickly I end spending so much money on buying bundles all the time .To top it off I was promised 1 Gig bundle every month when I renewed contract. A year later they claim there was no such offer. Even then it was such a hassle to get the one Gig I would always end up paying the ridiculers out of bundles rates. I really feel I am getting **********.