Flight Attendant's aircraft was damaged when the passengers were boarded with an improper bridge between the catering service truck and the aircraft.

Narrative

After the previous crew got off catering was on the plane swapping out equipment (galley carts; etc.). I was the AFT Flight Attendant so I went to the back of the aircraft to stow my bags and begin my preflight. I noticed as I passed the caterers that they didn't use the smaller bridge that I usually see them use when catering. The gate began sending passengers and after first class was seated and predeparture orders taken the First Officer came into the cabin and informed the passengers that their assistance was required. He requested that all passengers go to the very back of the plane and find a seat behind the wheels. On my way back with the passengers the forward Flight Attendant told me that apparently the catering truck was stuck. Eventually the First Officer came back and told us that they could come back to their original seats. He informed both Flight attendants that the door was bent and maintenance would need to come and look at it. It was later determined that the door was severely bent. Passengers were asked to deplane and we waited for a different aircraft.