lack of communication

I was on vodacom contract so I decided to settle the contract and move to prepaid. The data I got from my contract had depleted when I send through my cancellation quote so I used my own money to buy data. The moment they moved me to prepaid, my phone stopped working, no access to the internet was even granted. When I checked my balances, I realised the data I have bought with my own money was gone. When I called vodacom, all the consultants at the call centre told me that I used up the data I had bought the previous night because according to them, my internet was running the while time. So now I want to understand why I was never told that you forfeit all your data when you cancel your contract and why forfeit data that I bought with my own money?and why forfeit something that I paid for? Im going to block tgeir debit order until they respond and credit my data back and then i am porting to a more reliable service provider. I regret the the day I ever walked into a vodacom outlet and not to mention the clueless cakl centre agents who were quick to tell me how I had used up 500MB in one night