Change default calling app
You can download additional calling apps from Play Store. After you've installed one, you can make it your
default calling app.
1. Go to Settings > Apps & notifications.
2. Touch Default apps > Phone app.
Or, touch Advanced > Default apps > Phone app.
3. Touch the app to use.
Fix an issue
If you can't make calls, try these troubleshooting steps.
Contacts, calls, voicemail : Phone calls 120