Dr letter

my husband goes to PE from JHB every Friday and uses Mango, he fell ill and needs to be admitted to hospital so therefore could not fly today. I called into mango and said I have the letter from the Dr as well as the hospital they said they can cancel the ticket but they wont waiver the R370.00 penalty even if I provide them with the Dr and hospital letter... I feel they are been totally not very understanding ! what are you supposed to do if you not allowed to fly under Dr's orders ??