Unfair policy procedures 😡

I booked a online flight with eDreams and Fly safair for my 79 year old mom. I have send proof of Dr letter that I need to cancel the flight and get a refund voucher for the full amount but they want to deduct 50% or you i must pay an additional R300. I have gotten No where and I cant get a Manager from FlySafair to get back to me either. Service really sucks big time.