Overcharged for ticket then no assistance given

My dad passed away and after receiving a recommendation I purchased a flight ticket for my sister to fly from Durban to Johannesburg to support my mother. I live outside South Africa so it would take some time for me to get there. I paid the ticket, and when my sister arrived at the check-in counter, she was informed by Lift Airlines that we paid R1500 too much for the ticket. They explained that it would be placed in a wallet but she told them that I lived overseas and that I need to receive a refund to which they agreed. I contacted customer support various times via WhatsApp and email, and they told me that a team leader will get back to me, but no-one even bothers. I will never be able to make use of a wallet as I don't live in South Africa. I do not know anyone who I can transfer it to. My sister's flight was a once-off so she can't use it. I understand terms and conditions, but if the company is at fault for initially overcharging me for a ticket, they should refund me.