passenger seat belt jammed

If the seat belt motor is not locked, you can manually move it.
First disconnect the negative lead of your battery. Then remove the lower back seat frame. On the frame of the car there is an access panel to the seat belt motor. Using a hex key, turn the motor to the desired position.

The cost to replace this assembly is high.

There was a safety recall on this item. If the assembly was not replaced earlier, you might be able to get it replaced for free.
Even though I had mine replaced due to the safety recall, the newer unit failed a few years later. After much discussion, Mitsubishi replaced it for free.

Good luck.