Vodacom's unhelpful call centre agent

I took out a contract with Vodacom which was a top up at which point I enquired about how best to use the phone. I was told don't worry if you have wifi you won't be charged. Two days later all my airtime is gone, the in store agent refers me to the call centre, he has his sale, the call centre agent says oh you should turn off your data, something I have never had to do before considering I have wifi and was told that wifi would be just fine. They send me from one to another and they don't really care as long as they have their sale. Been loyal to Vodacom for more that 10 years and now I am sure that it's time to move on.