iPhone stuck in headphone mode and it preventing user from hearing the sound. Also iPhone acts like headphones are plugged in.
If you see the icon like this when you adjust the volume buttons, there may be broken piece or dirt in the headphone port.
Unplug and re-plug iPhone headphones several times (at least 8 to 10 times). Use hairdryer or toothpick on the iPhone headphone port to remove broken headphone jack or dust.
If you spilled milk or Pepsi like water, use q-tip (with the cotton ripped off)
Reset the iPhone. Press and hold Sleep/Wake button and Home button together until Apple logo appears.
Play a song (lengthy duration) and allow iPhone to completely lock.
Now insert iPhone compatible headset jack.
Unlock iPhone. Stop audio and unplug jack.
Plug in headset when phone is locked.
Hold down power button. It will bring “slide to power off” bar.
Now remove the headphones.
Press the “cancel” button at the bottom of the screen.
Now check the sound.
Connect your iPhone via Bluetooth to a speaker system.
Play a music.
Switch from speaker system back to Phone.
If you have any other issues or solutions, do let us via comment.