Robben Island Museum Stole my father's money!

My father visited from overseas and booked 2 tickets to go to Robben Island about a year ago. The trip for that specific day was cancelled due to bad winds. He only recently recovered the slip he received for the purchase of the tickets - asking me to do a refund for him. I have been struggling since May 24th 2019 for the money to be paid into my account. I have provided my account details and followed up numerous times. Pay back the money!!!!! Just to be clear who I am talking about - this is the link to their website: http://www.robben-island.org.za/tours.

I expect a swift payment!