UNBELIEVABLE

I was suppose to fly from Port Elizabeth to Cape town on Tuesday the 16th but I missed the flight because I was sick and had to go to the doctor early morning of that day . As I reached the counter was told that the gates are already closed and I went back to the counters to enquire about the next available flight and I was told that the ticket is valid for 6 months and I must either pay the penalty fee and the difference of that particular flight that i would use or bring the doctor's certificate. I decided to take the penalty route because I had no doctor's certificate. Now I want to use that ticket am told that i was suppose to give the indication in 4hours and no one told me ,now I have forfieted the ticket . And I need to use it ,this is disgusting