Incompetence

I was at Pick 'n Pay Clothing in Lambton Germiston 21/08/2021, I was so surprised that they closed the door at 15h45 which is not the correct closing time according to the trading hours written outside the door. I then asked the 3 staff that was standing on the floor you could even see they were ready to go by exactly 16h00 which is the time they supposed to close the door, the ladies (Pick 'n Pay Clothing staff)confirmed to me that they close the door at quarter to for them to cashup!! That really didn't make sense to me cos according to my understanding the door should closed according to the time that is written on the trading hours. Opening and closing time must be exactly the trading hours of the business not early and not late . I would really like to find out to the Pick 'n Pay management how does the closing time works because according to the explanation that I got from their staff yesterday I am very confused.