Avis enquiries

Good day I have taken out a rental with avis on the 25 March 2020 for 2 days at cape Town Airport and have to return it on 27march2020 at Langebaan avis car rental so I got a call from avis on the 26 march2020 asking me if I can bring back the rental on 26 March2020 and told me that they will refund me the 1 days money back but it never happen so am really disappointed in them. Rental number E***