RIP ing us OFF

As a prepaid customer I buy airtime and convert to data, 1 Gig at a time and at times 3 to 5 Gigs over 7 to 14 days option. A Gig of data disappears in less than 30 minutes while Im typing an email. Without warning dat is taken off my airtime until both balances (data and airtime) are zero. No warning like Cell C would do. When I complain I get back a Gig of data but Vodacom refuse to institute an early warning. I have requested that they terminate the use of data without utilising airtime and I was told the system doesn't allow them. In this current era of digital, its not possible? So there is no way I utilise a Gig of data a day. No downloads, just emails and the odd web search. Ive turned off all background programs and auto updates. Where does the data go to? Once again our Consumer Council doesnt pick up on these practices and puts a stop to this blatant theft.