Not willing to help the customer

I recently moved my Son's contract from AutoPage to Vodacom. He always received messages saying when his data bundle was about to be depleted, he would then buy another bundle. As it happens, the 2nd month after we moved over we got a R3500 bill! All of which was out of bundle data. On further investigation it was found that someone updated the number the sms was sent to. It was updated to send to my number! Firstly, we have no idea who did this (VC cant tell us either as it was done online apparently and we have never logged into the online system), secondly, I never received the message either! The next issue is that there is a limit on the contract. When mentioning this, VC say they are unable to enforce the limit on data as the session needs to end on the network before they lock the contract. Apparently the session never ended, and has still not ended. Even though we have WiFi that he connects to every day. Surely this ends the session? When on prepaid and your airtime finishes they are able to end your data session very quickly. Seems when its their money there is a concern, when its the customers then its of no concern. I want my money back and for you to fix your issues