Vodacom keeps *****ing my data

Yesterday mu husband bought me 30MB, I used it for a while on WhatsApp, then when I got to the office I switched it off and used my office Wi-Fi, by then it was 28MB. In the afternoon around 15:44 I switched off the office Wi-Fi and on to my mobile data, wrote a birthday message on my brothers FB wall. When I switched back to Wi-Fi I got an sms saying that my data is depleted, HOW? from 28MB to 0MB within just 2minutes of posting a message on FB. What ****ed me even more is that when I called their call centre 155, LULU or Lulama shifted the blame on me or my device S2, she asked me for another number to call me which I gave her, then she said I must go to about device under settings, then software update. then she asked if the was a tick on Auto Updates, I said NO the really was no tick, because I know all about this and told her before she took me on all this that my Auto updates are not ON, but she did not believe me. now that I told her the was no tick, all of a sudden the phone went dead and she never called me again. Then Vodacom sent me an sms asking how would I rate their service, I answered them on that sms telling them I would rate them 0 and will never ever recommend.