How to remove the seat belt holder?
 

I've got a rattle somewhere behind the plastic panel through which the seat belt holder comes in. I would like to remove that panel and dynomat all under there, but I can't figure out how to remove the seat belt holder. I can see there's a bolt that attaches it to the car body, and I tried to pry off the plastic piece at the tip of the seat belt holder but it refuses to come off. Has anyone done this already? What do I need to do?

Thanks