"RVS staff member"

On visiting the eye department block H for the first time with my mother, we arrived at 1.15 and proceeded to book in at reception situated right next to the RVS. There was a hand written note on the door of the RVS kiosk stating, "we will close at 1.30pm today". I asked mum to go and get a couple of cans before they closed. I heard the member of staff say to my mum, "we are closed now, ive cashed up". I turned and said to the member of staff, "its not 1.30 yet, its only 1.15" to which they proceed to shout across at me (even the recptionist looked mortified) "that makes no difference whatsoever". I ignored the shouting, asked my mother to sit down and carried on booking in at reception. Ideally i would have given that staff member a piece of my mind, but at 85, my mother wouldnt have liked the fuss. I cannot let this pass withought this member of staff at least being talked to about their non-communication skills. If they didnt want to be there, they shouldnt be working for you. Thank you.