are they trying to cheat us, the customer

The last 4 times i have been into clicks to buy baby supplies, or other household supplies this has happened to me. And i NOW think Clicks is doing it on purpose to rob us, their customer. The prices displayed on the shelf are correct, however when you get to the till and they scan the item, the price is more. Only when you question the price at the end, do they say you have to get the bar code price on the shelf, then they ring it up and change the amount. But I have 2 problems with this 1. People waiting int he que behind you, see you questioning the price, this makes me as a customer feel very insecure. 2 How many other people just except this and pay the price, will Clicks refund them their money. Today was the first time I thought I must use my own calculator to add up as i go along, and when i got to the till, I was under no surprise to see that I was over charged. I have been overcharged on the following: toilet paper, nappies, wet-wipes, baby bottles. It just makes me wonder for how long has clicks been ripping me off, and not just me what about all the other people (clicks customers) who don't actually check their slips. I have lost all trust in them now.