Unhappy Customer

Every month without fail , I received a call center, the number is *** which i assume is in KZN whereby they tell you story that Vodacom wants to reward you with more gigs at no cost. I decided to entertain the call in May and I have seen my contract increase from a 5gig to 20gig from a cost of R330,27 to R510,27 and R523,37. This is an increase of R1 000 as I have 5 contracts. I have e-mailed Vodacom on the 31/07 and 07/08 and i have not received a reply.