The headphone socket is an integral part of the microphone and receiver circuitry. The headphone socket connection between the socket and the mainboard may be suspect because of the fall. The following link is just to show you where they are. At 3:40 minutes into this video you can see the headphone socket connections - on the left of the camera module - the 5 tab connectors. https://www.youtube.com/watch?v=BoDI3dPL...
You do not have to take the back off the phone to do the following.
Try placing your finger and thumb, front and back of headphone socket, from top down, to about the level of the camera (i.e. finger on front of phone in line with socket and thumb on back of phone in line with socket) and gently squeeze.
Try making a call, with or without the headphone / microphone inserted and see if you can be heard. If not try a call while you are squeezing the headphone socket.
If you can be heard after you have tried this verify that it stays connected on future calls.
If you cannot be heard anyway it seems as if the voice transmission circuitry of you phone has been damaged. As the internal microphone is part of the mainboard and the external microphone does not work either it would seem that you will have to replace the mainboard or get a replacement phone.