Attempted overcharge Checkers Cresta Center

This is about Checkers in Cresta center. Today I bought a number of items at Checkers Cresta. The "Nice and Easy" meals were on special: Normal price R 72.99 and 2 for R 99. And I took 4. At the till I was charged R 82.99 for each!! As I had bought many items, I only realized I had been overcharged after I had already paid. I complained. The sales assistant/cashier took the frozen meals and went to check the price. Returned with the label showing the special. Then more back and forth and I was eventually annoyed and asked for a full refund and to return the items (they were probably thawing by now). It seems the refund will take anything between 24 hours and 7 days to reflect on my account. Very annoying, inconvenient and a waste of my time! Please note that I understand that mistakes happen and no-one is to blame. However, this has happened to me at Checkers Cresta (only at Checkers Cresta!) several times over the years. Once I complained to head-office, but they were unable to find my invoice/checkers card number and so completely unable to assist in any way. I had to go back to Checkers Cresta to claim the error/overcharge as I had only noticed it at home - very inconvenient! Why is it the one Checkers in Cresta where this keeps happening? How many people are overcharged and never notice?