I flew from Jo'burg to Cape Town flight 6427 on 23rd April 2014 at 16h00. My travel agent due to being diabetic always books me an aisle seat so I can get up and move for circulation. I also recently had a hand operation and this aisle seat helped me to keep my hand away from other passengers. I checked in and got the seat my agent booked. As I boarded I was told I was moved to a middle seat. When I queried this I was greeted with a bad attitude and was told they needed my seat for a disabled person. When I explained my medical condition and my operation I was told I could wait for another flight if I did not want to take the middle seat. When I got on the plane the person in my seat was not even disabled. When I approached the stewards my complaints was brushed aside. Poor attitude by staff.