No voice during calls via bluetooth C4 2018

[Greg147]

Citroen C4 from 2018, during a conversation after connecting via Bluetooth, I cannot hear the voice of the person I am talking to, only a fraction of a second of buzzing and then nothing. What could be the reason?
Sometimes it happens that you can talk normally, then suddenly the sound stops and you can't talk for a few days, then it miraculously repairs itself.
Now, since the frost, it has not been working for two weeks.

I will add that the radio or music played via Bluetooth or navigation instructions from Android Auto can be heard normally.
The microphone works, the interlocutor can hear me normally during the call.

Software updated to the latest version.
Maps updated to the latest version.
I tried reinstalling the software but that doesn't help either.
Factory reset does not help.
I tried to connect with three different phones. The issue still exists.

Does anyone know what could be the problem?

System version: 21/08/87.32_NAC-r1
Maps: 26.0.0

[GiveMeABreak]

You have the latest Firmware and Maps.

1) Ok, so can you list the 3 exact make and models of phone you have been testing.
2) Have you connected the Phone using a wired connection using CarPlay or Android Auto (disable Bluetooth temporarily) - and is the same problem still showing using this method?

[Greg147]

1. Huawei p40, Xiaomi mi 11, Maxcom mm135
2. While i'm trying to call by android auto with distabled bluetooth, car screen shows " no bluetooth connection" and i have to use phone speaker

[GiveMeABreak]

Ok, so unfortunately it is likely to be the phones - none of those Chinese phones are officially supported.