OTA 5.1.1 gone wrong. no sound during calls anymore iPhone 4

A few days ago my wife applied IOS 5.1.1 (OTA) the update completed and the phone rebooted - after this all seemed fine.

later that day she realized that her phone didn't get any audio anymore during phone calls.

(people on the other side cannot hear anything and on her phone you cannot hear anything either.)

It's great that the iPhone can do everything - but normal phone calls are still essential right

All other audio operations are fine btw, voice recording/ speakers, music, face time  all work as normal.

Although they do have different audio processors but still what is the chance of that breaking during/after the IOS upgrade.

I already tried the following:

- reset/restore to previous backup.  didn't work

- downgraded the phone back to IOS 5.1 / setup as a new phone didn't work.

- downloaded full IOS 5.1.1 and upgraded again, no fix.

- reset to factory settings and setup as a new phone.

The phone is now 1.5 years old and out of warranty.  (as usual)

A call to apple support - We cannot do anything as it is out of warranty.  try restoring it ..  great!

Now I accept it is out of warranty for real hardware faults, but it was working perfectly until Apple prompted/pushed me to update.

(after which it rebooted and stopped working) 

To me this seems like a software/firmware/hardware bug that is being exposed due to the update. 

The phone has never been jail broken either.

The fact that I see threads on the forum that are 170 pages long about similar audio issues doesn't fill me with confidence that apple will do the right thing and own up to the problem or fix/replace the phone.

https://discussions.apple.com/thread/3404857?start=2535&tstart=0

But you never know, so here is my post.