Really disappointed

My mother did an early upgrade with cell c 6 months ago and the agent that assisted said with the deal that we want, we will get 10GBs of extra data for the first 6 months of the contract which starts on the 7th March, my mum even called the call-centre and even they said that she was supposed to get 10gb data so they logged a case. We then visited the store where she initially upgraded her contract only to find out that agent that helped has resigned. The other agent that assisted us phoned their help-desk and asked about this and help-desk said it wasn't part of that particular contract. Only reason my mother upgraded to that package was because of extra data otherwise she was going to cancel. She went in today asking if she can cancel her contract due to her not getting that data, and they simply told her if she does then she has to pay for the phone.