Warning About Shops

This is going to be a rant. I'm sorry!
After working in a shop in my twenties I automatically add up prices as I shop and by the time I reach the till, I have a good idea of what I will be paying.
Beware of W.H.Smith's in Barnet- for the second time in two weeks I have been charged much more at the till than the price on the shelves. This is nothing to do with alterations in Value Added Tax- the amount is too much for that. I had to get the assistants to check both times, which was a time-consuming fuss and seemed to cause a degree of resentment on their part.
I am not going there again. This is very similar to the trick that Sainsbury's in East Barnet regularly played on its customers- stacking goods that were the normal price very close to 'Two For One' offers, making it easy for a customer to make a mistake and buy two full-priced packs of whatever. After having to check my bills time after time, and challenging the store staff about this misleading practice, forgiving them, going back and having it happen again (and again), I've given up going to that shop too.
I actually think this is stealing from customers, isn't it?