Yes, you may change the drop or pick up location. But you will have to notify much before the scheduled pick up and drop off. The drop-off and pick up services understand that you may need to change the location according to your travel plans and they will accommodate accordingly. But if you share the ride with someone, the pick-up and drop off location may not be that easy to change without the approval of the other person. You might have to wait in case the driver gets delayed in picking or dropping off the other passenger.