Pakistan International Airlines [PIA] review: customer service 1

On Sunday 29th December I had to fly back to the uk with my poorly son from Islamabad airport. My. Son needed blood transfusions on Monday 30th December, and due to the awful poor customer service from PIA I was unable to get on the flight I had paid for.
There was a full whole hour left for the plane to take off and I got refused to be checked in I got told I was late. When I'm fact I wasn't I arrived at the airport 4 hours before.
There was flights that were delayed when i got arrived at the airport, the ques were actually to the car park that's how busy it was on that day.

They were letting people through when i got to the check in point and when my luggage was on the belts i got told i am late, i only had 1 suitcase as well not like i had plenty.
PIA staff knew I was desperate to get back to the uk due to my sons illness instead they said to me pay us £500 and we can get you on the next flight that's leaving in 5 hours. Which I had no choice but to do as my sons health was very important. PIA staff are very corrupt and good at making money out of people when it's not there fault. Therefore I want to take things further as how I got treated was very wrong so can you kindly put me in the direction who is the head of PIA.