Closing store before time

I went to Pick n Pay Clothing on the 10/05/2018 at approximately 19:45, now I know they close at 8pm so I rushed to get there on time. The doors were closed! I signaled to the cashier to ask if he was closed and he said yes but I pointed to my watch claiming that it wasn't 8pm yet. It's not like my watch is ahead of time as my cellphone reflected the same time. I was ignored and not let into the shop. I can't understand why you would close 15 minutes beforehand, how is this acceptable? I complained on Pick n Pay's website contact us page to which I received no response or even an acknowledgment , such bad customer service!