Data theft

Since January the 1st I've spent R800 on extra data for two phones . When I phoned the data centre number to query they told me that majority of the data on one of the phones is being used by Twitter . That is my wife's phone and she doesn't even have a Twitter account never mind the app on the phone which she doesn't have either. The they gave us half the data back on our last purchase so my wife got 500mb and I got 250mb . How on earth can one spend R800 on data which is being used for whatsapp and Facebook. Not watching videos or playing games or downloading anything . We've had contracts for almost 4 years now and we have never had this problem 1 gig would last us a month . Vodacom is clearly *****ing from their customers and doing nothing about it . Time to go to MTN I think. ****************