Clicks constantly charges higher prices at the till from the price on the shelf

Clicks is a constant issue of the items being marked one price on the shelf and I get charged more for the products at the till. I usually check that the 3rd item in the 3 for 2 has come off the slip but always find that the individ. pricing was wrong.

Usually I return for a refund but the trouble it takes to go back to store is a huge bother and staff take ages to process the refunds.

In the long run I am loosing tons by shopping at clicks