Checkers not responsible for pricing errors

In their Easter Promotions that started the 25 March, Checkers advertises Lindt Chocolate 200g for R 59,99. On the 28th March a purchased 4 boxes of Lindt. When I checked the till slip at home I noticed that I was charged R 86.99 . I phoned the store /- 10:00H to speak to the Manager. I was informed the Branch Manager is on the floor with the Regional Manager and is not available to speak to customers. I explained the problem and requested the Regional Manager to call me. By 14:00H nobody has called, I called and spoke to the Branch Manager. She made as if she did not know of my previous call, she then informed me that she had more important things to deal with and Checkers policy is that it is the responsibility of clients to check the prices they pay. I pointed out to her that the promotion had already been on for 3 days and by now Checkers should have picked it up, she informed me that it will only be the one till that I paid at that will be wrong. This can not be true as all tills are linked to a central databases. She told me if I want my money back I have to come into the store and it is not Checkers responsibility to sort it out as they already have my money.