wrong data billing

Between the 6 and 8th of May 2015, I was in a conference and I was logged onto wifi. On the 7th of May, I started to receive notifications that my data was being used up so I made sure my cellular data was switched off and I even switched my phone off and then put it on again. On the 8th of May, i received a message saying that my soft lock was reached so I called Vodacom because how can I be charged for data when my cellular data was being switched off. when I called 082111, I was told Vodacom is having technical issues but I have to call 082155, which i did and they were suppose to investigate and get back to me. Just for the 7th I used up all my data bundle was apparently charged R268 becauase there was still a connection even though my cellular data was switched off.Thanks to snapshot I have evidence of these calls and the duration. Today when I called 082155, they have no record of my query and said I need to call *** as they have logged the query, which they transferred me to, after 42minutes on the line, I still have no idea whats happening and I was told to call 082155 again...I am really tired of this pathetic service from Vodacom