Some Lumia 920 Users have reported a problem in which the phone suggests that the headphones are still plugged in, even when that isn't the case. There are a couple of ways to fix this. Below, we will give you some tips to help fix your headphone jack on the Lumia 920:
Steps:
1. Plug in your headphones into your phone.
2. Make a phone call with the headphone plugged in.
3. During the call, you should turn speaker modeon and off .
4. Unplug the headphone from your phone again. It work.
If that doesn’t work for you, then try the following:
1. Connect a standard Nokia hands-free headset (if you have one),
2. Now, make a call to any number
3. Finally, disconnect the hands-free headset during the call. It should work.
If that didn't work, either, try this:
1. While plugging in the 3-conductor headphone, do not insert it all the way in at once/.
2. You should just make contact until you can hear the music/sound from your phone on the headphone.
3. Then, insert the plug all the way at once with a click, it should the work.
If those solutions don't work, try calling Nokia customer care.
Steps:

1. Plug in your headphones into your phone.
2. Make a phone call with the headphone plugged in.
3. During the call, you should turn speaker modeon and off .

4. Unplug the headphone from your phone again. It work.
If that doesn’t work for you, then try the following:
1. Connect a standard Nokia hands-free headset (if you have one),
2. Now, make a call to any number
3. Finally, disconnect the hands-free headset during the call. It should work.
If that didn't work, either, try this:
1. While plugging in the 3-conductor headphone, do not insert it all the way in at once/.

2. You should just make contact until you can hear the music/sound from your phone on the headphone.
3. Then, insert the plug all the way at once with a click, it should the work.
If those solutions don't work, try calling Nokia customer care.