Special Price "*******"

I went to Pick n Pay Bluff yesterday. They had the PnP brand of yoghurt 1kg on special. The sign said PnP Double Cream 1kg Yoghurt ASSORTED for 19.99. There was 3 flavours available. Plain, Strawberry and Lemon Meringue. So I picked the plain and the lemon flavour and proceeded to the till. The swiped the plain at 19.99, but the lemon meringue at 29.99. R10.00 more!!! I explained to the supervisor and manager but they insisted that only the plain was at 19. 99. I waited with my wife and twins for almost 20min, only to be rejected again. but the sign said ASSORTED. So how can ASSORTED mean only one flavour. That is very stupid. I feel that it was a total rip-off and false advertising. I am very disappointed.