Here are some common reports you can build with the Phone Numbers object. If you can't see the 'Phone Numbers' report type in Salesforce reports, you will need to enable them. See this guide for how to do that.
Which phone numbers are assigned to users as DDIs?
- Report type = Phone Numbers
- Show Me = All phone numbers
- Filter on Natterbox User not equal to "" [blank]
- Add in the columns: Number and Natterbox User
- Optional:
- Add the fields: Country or Area
Which phone numbers are being used in Routing Policies?
- Report type = Phone Numbers
- Show Me = All phone numbers
- Filter on Call Flow not equal to "" [blank]
- Add in the columns: Number and Call Flow
- Optional:
- Add the fields: Country or Area