Menlo Park Post Office Closed on a Saturday

I went to the Menlo Park Post Office today, Saturday the 6th of Feb 2021, to collect a parcel. I got there and the Post Office was closed, even though the trading hours online and on their door say 8:30am to 1pm on Saturdays. I then went to the Menlyn Retail Park Post Office to find out why the Menlo Park Post Office was closed, only to be told to go back to Menlo Park on Monday. So again I ask, why is the Menlo Park Post Office closed today (Saturday 6th of Feb, 2021), contrary to their displayed trading hours??