i think what vodacom is doing can almost be theft

my wife has multiple contracts with vodacom. we buy 2gig data every month on a contract. we used to be able to accumulate data for 3 months before you loose the first months data. i don't think it is fair that we should loose data if not used. its called saving. its like i buy rice at a shop and if i didn't use the whole bag by the end of the month the shop comes and takes it back and resell the rest to some one else. this is theft. i paid for it. its my data. you may not take it back. it against the consumer act. please respond to this for i am going to refer this to the consumer board for action.