Key in door, turn to unlock, when you meet resistance, forcefully keep turning key and try handle, be advised that the doorpin will not necessarily pop up

if you have the door card off, push and pull the lock arm from the lock a few times, its the on were the lock has a metal arm, may need to remove a metal plate to get to it push door at same time. when door opens take the lock off and give a good clean out and re grease up then try it with a screw driver or metal rod or even a bic pen and make sure it works before putting back on.
also dont slam your doors any more....