Bad customer service

Spar Morningfield in Parklands, the manager is very rude, he doesn't customer service at all. They put a price for 1L tonic water as R14,99 and that of ****** ale R18,99, but when I get to the till the tonic water rings R18,99 and I said but that's not the price on the shelf. The manager was so rude and told he won't give me with the price I saw. I find him very unprofessional and shouldn't be a manager.