Vodacom Smart Tablet Deal - Incorrect Billing

I recently took out two Vodacom Tablet deals (Smart Tab 3G). In May 2015, the advert in the store and magazine was R79 p/m for a 500MB top up data deal and tablet. I see this month, the deal is now R89 p/m. However my June Bill states amount due is R113.00 for each line? When i called the call center, i am told the system says i have a 500MB top up package but must also pay for the handset? When i explained that it was a package deal, i was told to contact the Sales department and ask them to explain. When i called the Sales Dept number, a lady by the name of Busi answered. I explained the situation to her again to which she replies i must go to a store because their prices are different. When i ask who i can escalate my complaint to, she says they don't have a complaints department. I must send an e-mail to customer care. Although R24 p/m is nothing in the grand scheme of things (difference between invoiced and signed for) the attitude of Vodacom Sales staff leaves much to be desired. I have 6 lines with Vodacom. One is due for upgrade - I have just cancelled it instead. The rest will follow suit. Not impressed!!