The shop changes the prices

I went to the Vodacom shop in Ermelo, Limatra, wanting to buy a Vodaphone tablet. It is advertised for either R59 per month or R1000-00 cash. Firstly the lady didn't really want to sell me one cash because according to her they prefer to keep it for contract clients. She also informed me that should they sell one to me cash, they will be asking me R1 500-00. That is *****!!! They can't change the price to suit them, especially when it is 'n price fixed by their Head Office. I spoke to someone at their head office and they also said they are not allowed to do so but wanted me to drive all the way back to the store to let them phone them. There are no contact details for the Ermelo shop so that I can phone the manager. The sales person's attitude is ****py and I expect them to keep to the prescribed prices.