Closure of branch without an explanation or apology

I got to the post office at St Wendolins and there was a hand written note stating SIVALILE TODAY Saturday 12 May 2018. According to my knowledge the branch trades on Saturday from 8am to 1pm. The was No apology for the inconvenience and no explanation as to why the branch was closed. I had an urgent parcel delivered to that branch that I needed to collect, and I work during the week so the weekend is the only time I have to collect it.