Terrible service and incorrect pricing

I phone Mtn waterfall mall on Monday 17 August 2015 to find out if they have stock on the Sony Xperia Z3, they told me no but will receive stock on Wednesday 19 August. I asked the person for a cash price on the phone and they told me the cash price is R8700.00. When I phoned them again on the 19th to confirm if they have stock Lerato told me yes and they have the white one I want, I confirmed the price with her that was given to me and she said yes approximately. My mother went there to buy the phone and she was told that the phone now suddenly cost more than R11000.00. ***, how can you give a client a cash price and then suddenly tell them there is extra costs that needs to be added for who knows what. This is pathetic and I hope I never have to deal with a person or company so *********** of delivering a service ever again. Very unhappy client. Doreen