Originally Posted by
kchika
Beware - I was assigned a G seat last time and was supposed to have the whole row of 4 to myself (flight was only 30% full), but Mr. Selfish decided to sit in D and asked me to move to one of the rows of 3 in the back. I was in no mood to argue with him and moved myself...

i've been in that situation b4. your approved seat blocking is in the flight manifest, call the FA / ISM and they will sort out the other fellow.