Data disappearing

I have called Vodacom about 7 times, been to the store 2 times and called the store 2 times. My data keeps disappearing from my phone. Vodacom can't tell me where it went. 1GB runs out in less than an hour. All roaming etc data is turned off. Most on my applications are set to use wifi only. The keep on sending me smses saying "Dear Vodacom Customer, we trust you enjoyed the service experience. Your query with ref number # has been closed. We value your continues support as Loyal Vodacom Customer" I'm sooooo fed up and nobody can help me! What type of Company is this that steels your data!!!! When this contract is finished I'll make sure we take all our business elsewhere!!!! I'm sooooooo mad! Can anyone please give me any recommendations on what to do.