Shop Not following trading hours.

I was not happy with the way PEP at Riverwalk shopping center in Potchefstroom treated us as customers. The trading hours says from 9am to 6pm but they close their doors at 17h30 and refused us to enter around 17h40. If they want to close early they must change their trading hours to 17h30 then. I was not impressed at all with their behavior.