If you want to make calls on the LG smartphone, you usually use the pre-installed system app "Phone". However, alternative phone apps such as dialer can also be installed on the device. To ensure that all calls are routed via the new desired app, this must be defined as the default app.

Android 9 | LG UX 9.0
Step 1:  Open the  Settings
Step 2:  Tap on  General
Step 3:  Tap on  Apps & notifications
Step 4:  Tap on  Default apps
Step 5:  Tap on  Phone app
Step 6:  Choose desired  Dialer app
  1. Open the Settings
  2. Tap on General
  3. Tap on Apps & notifications
  4. Tap on Default apps
  5. Tap on Phone app
  6. Choose desired Dialer app

LG Instructions