*****ing Data?

My mom, who has been a Vodacom customer for years and years. She upgraded a couple of months ago (probably around 6 months or so ago) The past 2 months and keeps receiving smses from Vodacom telling her that she is running out of data. She loaded R200 worth of data, the next day it was gone, my brother then loaded another R200 worth of data the next day, which also didn't last the day. She then loaded another 500mb data, and not 2 hours later she received an sms to say she had less than 50mb left and needed to reload. In which time she did not even use the phone.

She tried to go to a Vodacom shop, to try and find out what was happening, but they were unable to tell her and were very unhelpful!

This has been very bad service, she is a pensioner and she feels like she wants to cancel her contract!