Why is Viber Call quality always Average?

[WPCentral Question]

Hey. I have Nokia Lumia 1320 and I always see Viber Call quality: Average. Sometimes the voice is really good, but sometimes is bad. However I always get the note that Call quality is Average. Maybe somebody knows what the problem?

Reinstall didn't help.

 

[hwchain]

This is the problem of every windows phones.