Taking Advantage

I shopped at Village View Woolworths yesterday, and would like to know why the prices on the tags or on the shelf on certain items are not the same when it is scanned at the tills. I purchased two shopper bags on the tag its R 25.99 at the till R 29.99. Mini BBQ chicken kebab on the item R 28.99 on my slip R 29.99 Assorted nuts, on the shelf R 70.99 on my slip R 79.99. This is terrible service!!!! Why are you taking advantage like this and we only realise when we get home and compare items with the slip!!