It is probably jammed because of major damage or decay to the structure of the car, such as a rusted A, B or C post, or sill. It may well not be safe to drive, so if you are outside the car you have no interest in getting in; or if you are in the car, exit through the other door. Or if the problem is just that the lock is jammed, call an auto locksmith, or put a brick through the window. All of the above assumes that it is your car and not somebody else's. In which case go to a police station and hand yourself in for attempted grand theft auto.