Which is right?

My ears pricked up in a clothes shop today. An assistant was replacing a promotional poster because of a "spelling mistake"!  It wasn't me who complained, honestly! Well done to Viyella/Country Casuals for reprinting and replacing.

Someone cost the company because they didn't know the difference between complimentary and complementary! I enjoyed a complimentary glass of shloer. They didn't offer me any styling tips though. I'm obviously a lost cause.