Galaxy S4 no sound during calls

Is bluetooth on? Might you be paired/connected to some bluetooth device? Turn off bluetooth, reboot phone, try again. Try with wired headset. If all those fail, then you are likely having a hardware issue. If the phone is under warranty then AT&T will swap it with a refurb phone assuming it is not otherwise damaged (ie, no water damage, no broken screen, etc...)

My S4 just started doing this in Sept 2014, after working fine for 18 months. I wonder what triggered it.

Silent phone calls, both ways. A reboot fixes it, but only for a while. Probabl not a Bluetooth issue, as I have experience the fault with BT off.

I just got a system update OTA from AT&T yesterday (Oct 20), so I'm eager to see if this fixes that problem.

The OTA seems to have fixed my horribly laggy camera. That's nice.

Any update on this? I have the same problem, only occurred after the latest update : I337UCUFNI1.

Pretty much have to reboot my phone to make or receive a phone call. After the reboot I typically get one phone call through.

I haven't seen an answer yet. I also only have the problem since the I337UCUFNI1 update.

Having the same issue .Reboot fixes it but its tiresome. Any solutions to this problem

I fixed it be resetting my phone to factory defaults. A huge pain of course as I had to re-setup everything on the phone, but it fixed the issue. As it hapens about a week or two after doing that AT&T released 4.4.4 which might have fixed it also. Did you receive that update and apply it? Anyway phone working correctly now.

This is exactly what's happening to me.  I get one good phone call, then if I don't restart my phone, there is no sound on either end of the incoming or outgoing call.  It takes time to continuously restart the phone and is very frustrating for me and the people trying to call me.

Julie

Try Factory Reset in settings.

Doesn't matter if Bluetooth on or off.  This happens on both my S4 and my wife's and ONLY started after the 4.4.4 update.  This is all over the place, why does ATT not have a fix for this because it is obviously a software issue since I mentioned this only started after.

Wait. How was this response from Ace - Professor considered an answer? This is NOT an answer to my problem (although I appreciate the effort.)

Also, the notion of a factory reset *may* fix the problem, but I'm not interested in going nuclear. A factory reset is a scorched earth fixing method, and leaves all of your setup efforts in the dustbin. It would take me about 8 hours to get all the apps, content, and settings back into my phone after a factory reset...and there is no guarantee that this will work.

In fact, I doubt a factory reset would work. This seems to be a 4.4.4 problem than many AT&T S4 owners have.

If I had to do a factory reset on a phone that's more than 1 year old, I would instead solve the problem with a new phone. If I'm going to invest 8 hours, I may as well invest a few hundred bucks, too, and end up with the latest.

So that's actually what I did. I'm now waiting to receive my Motorola X 2014 Pure Edition. No cruft and bloatware from AT&T, faster Android updates. Cost me a pretty penny, but F these guys.

And BTW, my phone is STILL losing phone call audio, even happened today.