Voice quality issues may be related to the battery optimization feature on your device.
Suspended apps get cut off from network access because of this feature, which causes voice quality degradation on your calls.
To fix this issue, please follow these steps:
navigate to Settings > Battery
open the overflow menu(...) in the top right corner
choose Battery optimization
Toggle Not optimized to All apps.
Find the Yolla app, tap it and then choose Don't optimize.
