Detail not discussed properly when upgrading an ac

I went to Vodacom Westgate dt th end of May to upgrade my account. I have been on a package that have included BIS. I up-graded to a Samsung phone and was told that BIS will not be available on my new contract, which was supposed to start on 01/06/15. <br> <br> I was under the impression that BIS will still be activated until 31/05/15. Apparently that was not the case, but it was not explained to me. I went back to the store twice to try and find out what was going on. The second time I spoke to a manager (I think his name is Johan). He explained to me that my BIS was taken away the moment I started using my Samsung. I have been using the internet due to the fact that I did not know that BIS has been de-activated. According to Johan a credit would have been passed on my account due to the fact that the salesman did not explain the contract properly. The credit should have been around R128.00. On my last invoice, no credit appeared, and I was billed AGAIN for BIS!!! How can I be billed for something that according to Vodacom, is not available?