Air carrier First Officer reported the chocks were removed with no communication and as a result the aircraft; began to roll and was damaged.

Narrative

Aircraft rolled forward after chocks were removed; resulting in damage to fuselage; wing root; and air stairs. No injuries were reported.We had just settled into the flight deck and about to start our Preliminary Flight Check Procedure. A thump was heard and felt; followed shortly by the aircraft starting to roll forward.When we discovered the aircraft was moving we both simultaneously applied the brakes. The #4 AUX hydraulic pump was selected on; which gave us hydraulic pressure to stop the aircraft and set the park brake.The air stair used is mounted to a truck with stabilizer arms deployed after it's in position. Damage to aircraft was due to the air stair truck sliding against the side of the fuselage and impacting the wing root area as the aircraft rolled forward.Cause: The chocks were removed with no communication from the ground handler. Aircraft was not connected to a tug.Considerable force was required to remove the chocks; I believe a vehicle or small tug was used to pull them.Company SOP is to release the park brake after engine shutdown when chocks are confirmed to be in position. The aircraft sat for several hours while being unloaded and the hydraulic system had bled down including accumulator pressure; which is normal for this aircraft. On this aircraft hydraulic pressure is required to utilize the brakes including setting the park brake.Suggestions: Preventative measures could include better communication from the ground handlers that chocks are being pulled. This is especially important with contract companies who handle several different companies with different procedures.Revisiting the company SOP of releasing the park brake during the shutdown procedure after chocks are confirmed in position. Leaving the park brake engaged would have prevented this incident from happening.