Incorrect information resulting in huge bill!

Once again I am *****ed by Vodacom! I went for an upgrade to the Vodacom shop in Mall@Carnival, my Blackberry phone was not working anymore and I had to do an upgrade in beginning of September 2015, the person that assisted me told me and my husband that the BIS service was discontinued and it does not help me taking another Blackberry phone I can just as well go for another phone, as you can imagine i was disappointed, because you get use to the BIS service! I decided to take a Sony expiria with 120 free minutes and 300 MB top up so I know my account will not go higher than the monthly fee and I was told I will be migrating end of September and will then go onto my new package, I was never told be careful when you use your smart phone you will be charged for the data! To my horror I received a phone call from one of your call centre agents that my bill for data usage is approx. R2500 and he also told me BIS is still alive and kicking! This is now the second time I received incorrect info from the personnel at the mentioned branch. I am a customer and expect the staff at the branch to give me the correct details. At this stage I do not want to use Vodacom anymore!