Incorrect data bundle

I get every month 1gig data for the last two months i only got 500mb but was charged for a 1gig<br> Yesterday i logged a complained with vodacom as i am not going to pay for the data bundle which i haven't received got a sms yesterday stating that i have received a 1gig data promo when i called vodacom to ask what the problem was and why i only received 500mb 2 months in a row that said to me its because of its in the middle of the month etc etc etc etc, i asked if i must now pay for the 1 gig promo i received extra yesterday which i have not requested or have been called 1st and said this what we can do but you must pay for it NO just send it and i the client will pay for it i feel the service is bad and i want a exploitation why i have not received my full 1 gig for the last 2 months and why have my account been billed a extra 1 gig and i must pay for it without 1st calling me and explaining it to me. Vodacom is *****ing from me and im really not happy or thinking or will continue using there services after my upgrade is due in 3 months time.....