Sangoma Connect Mobile App Voice Quality Guide
We expect the voice quality to your hard wired desk phones to be perfect. If it is not, CALL US! We will handle and clear any network issues.
Yet, maintaining voice quality to mobile clients is a team effort. The reason is simple. It's your phone and your wireless carrier. Also, Infotel Systems may not have control of the the wifi system.
Please review below three screens on our smart phone mobile app.

Call Display Screen
While on a call, click the blue icon.
The Call Quality screen displays.

Call Quality Screen
Jitter must be under 100ms
Packet Loss must be under 5%

Network Preferences Screen
Set "Prefer Mobile Data" for shared/public WiFi
National Provider VoIP Quality Guides
Ring Central Mobile Issues
A Ring central app called "Ring out" forces outbound calls over cellular. They also list detailed instructions for clearing voice quality issues.
8x8 Mobile Issues
They provide very detailed instructions for voice quality issues. They also include call quality stats on their mobile app to help troubleshoot network issues.
Mitel Voice Quality Troublshooting
Mitel offers this "brief" 8 page guide and this huge 72 page manifesto!