Refusal to postpone or refund for an unforeseen incident

I was hospitalised due to illness and could not go there on the day that l was supposed to go. I sent them an email to inform them that l would not be able to come on the booked date as l was admitted in hospital. Their response was that they would not be able to cancel or postpone my reservation. l even sent them the hospital letter after l was discharged but l got no no response from them until now. Its been a week now.