iPhone 6 - The microphone / speaker does not work during calls only

Welcome
My dad bought an iPhone 6 from a friend who used it a day, it seems that the microphone and speaker after the update have stopped working.
I took to check the phone and in fact the speaker and microphone do not work but only during calls. Siri, voice recorder, messeger and other applications are all OK, the volume keys work, Siri hears what is being said, when using WatsApp, everything works. Only when we talk normally do not hear anything, neither hear me nor I can not hear anyone, total silence. The first thing I did was I quickly hooked it to iTunes and I did the restore without any copy to set up the iTunes phone as new, nothing helped. On the internet, I could not find anybody to have such a problem, usually when the microphone or loudspeaker was not working anymore, but only during a conversation. Anyone have any idea what else could be done? Downgrade some? It is possible ?
The phone itself visually looks OK, the original screen also has all markings.
Edit I managed to insert a card from the T-mobile with which the WiFi conversation works, when talking to WiFi support everything works, it looks like it does not work only during GSM connections.

Play soft but it is very possible to damage the connection of the CPU with the audio codec and the Baseband circuit on the i2s line. The audio data during the cellular connection (GSM) goes just after the i2s line from the processor to the baseband.

I tried to play soft and set it as a new iPhone without downloading any copies. Unfortunately, no result, thing to do or rather not profitable anymore?

it's not the software's fault. To replace the microphone itself or the entire system connector. greetings

But what does the microphone have for this since it works, all applications are ok, the speaker and the microphone work, the only problem is when the connection is to be made with Gsm.

Check first if it works on the headset.

of course, it was one of the first things I checked on the headphones Jack and BT, in each case the same, in applications the headset works during GSM calls silence in both directions.

Hello,
I have the same problem on iphone 7plus. Everything worked as it should. Today, some update and end. Music works. On the headphones works and how you want to normally get it back and forth silence.
Please help
Artur

Artoor78 wrote:

I have the same problem on iphone 7plus

The most common problem here is codec audio and pcb - broken connections with the system.

Hey ,
Did you manage to solve the problem in iPhone 6?
I have exactly the same problem at home.

@RafalB What can the amount of repair of such a line be?

Hello. Has anyone found a solution to the problem? For me it is the same, the phone has been serviced, the tape has been replaced with a microphone. Siri, voice recorder, notes - they work. The problem occurs only in conversation, I hear the interlocutor and the interlocutor does not hear me.
iPhone 6 128gb

Then you have a different problem. We do not hear the interlocutor and the interlocutor does not hear us. If you have an Orange card, check if everything works for you via wifi calling.