Refusing to honor advertised deal

I went into a Vodacom4U in Cresta on Sunday 1st Feb and got an upgrade on my current contract. In the brochure which specifically states that the deals are valid until 6th Feb there was a deal for a Huawei P7 which included a R 500 cashback voucher. My wife picked up the phone a few days later but did not get the voucher. I went back today and Siyabulela Nyati (the ambassador for Huawei) told me that this deal expired on the 31st of January. Firstly this is in contradiction of the adverti*****t in the Vodacom brochure which states that the deals are valid until the 6th of Feb, secondly when I was in the shop on the 1st of Feb Zanele talked to Siyabulela and he told her that everything is fine and I will get the voucher.