ADVERTISING WRONG AT WRONG PRICES

i have recently purchased iphone on istore pre owned the phone was on sale for R15999 paid that amount and i received my order purchase . yesterday i enquired about when will the phone will be delivered i was told i will get tracking no before the end of yesterday and phone delivered today . to my surprise i didnt get that so today i enqired again amd i was told my balance is outstanding with R4000 i asked how because thats was not the price i saw. then my order was cancel and told refund will be made between 10-14 days . i asked if i can get a voucher and purchase straight at istore and i was told NO. such inconvenience as i had to wait from wednesday to hear all this about my purchase . if my orderwas outstanding why was i not informed that same day or even yesterday when i reached out. instead they be advertising what they dont have need alone cant acknowledge the mistake was from their side .very DISAPPOITED WAITING FOR WHOLE 2 WEEKS FOR ITEM I DIDNT EVEN GET .ORDER FROM THEM AT OWN RISK