ahhh i had this problem before! its not actually a problem, i had to destroy on to find out how they work!
ok basically there is a little ball inside them which moves and locks into place in a certain position (ever notcied the belts lock up if trying to reach the glove box whilst going round a corner (as a passenger of course)?) so to get the belt out you need to actually fix them into the car and then they wil pop straight out..obviously making sure you've got the handing correct..
that should do it