Not hearing incoming calls

SOURCE: Motorola L6 - I could hear but the caller/receiver could not hear me.

Is the phone under warranty? If it is send it to Motorola.

SOURCE: Can't hear caller's voice

Turn up the volume control.  Don't have the manual in front of me but go into phone settings and look for the volume settings( not the ringer).  Check in your manual, you'll find it.

SOURCE: Nokia E90 Communicator - callers can hear me but I cannot hear

Not certain... but you need to check menu - tools - settings - general - enhancement and make sure your default is set to "headset".
When you plug headphones only (not the headset/mic combo) into the 2.5mm jack, it will go into a headphone mode where you can hear through the headphones but you must speak through the phone microphone - it sounds like it is going into that mode on you. It can only be the setting above or possible a short in the jack (though that doesn't really explain why it is happening only when you receive a call).
If you have 2.5mm headsets (or can pick up a small 3.5 to 2.5 adapter), you can also try having them call you and see if you can hear through the headphones - that would prove it is going into headphone only mode.

SOURCE: Cannot hear incoming call or caller cannot hear me

cannot hear incoming calls or outgoing calls

SOURCE: Phone: Samsung Propel Problem: I

Mine also did this. It only does this when you do not have signal. If you do have signal and it still does this you just need to call ATT and confirm it with them. They ended up sending me a new one that has better software on it for free.