Unhappy Woolworths Customer

I purchased a perfume gift set from Woolworths, it was their brand. I always use this perfume so I had an open bottle, which I decided to finish before opening the new bottle 100ml, 14 September took out new bottle to use and I see it wasn't working, no spray at all, took it to Westwood branch to do an exchange, they said they can't change it there I need to take it to Gateway branch where I purchased it. I took it to Woolworths Gateway was told that they did have a problem with the perfume where the pump wasn't working, was asked to go to customer service with the new 100ml bottle, at customer service was told I had to pay a difference in price, because I bought it on special at R429 snd now the price was R499 I had to pay the difference of R70. I didn't think that was right as it should have been just an exchange and not paying a difference, I did bring in the full 100ml perfume to return and they did say there was a problem where customers experienced the same problem. So it should have been just an exchange. It is not about the money but more about the principle behind it. Since it being a Woolworths brand perfume. We shop regularly at Woolworths!!!