Click on the "Telephony" tab and click on "VoIP Carrier" option.
Keep the VoIP Carrier as "Manual" and add "Voxtelesys" as the description.
Set up the code rules. If you select the "By Prefix" option, type "1" for the prefix.
If you select the “By Pattern” option, type the character ‘x’ ten times to match calls with 10 digits.
Select "Finish" and the trunk will be added!
From the "Extensions" tab, go to the admin settings of the user you wish to add the DID to.
Within the SIP Settings, go ahead and assign the DID number into the "Username / DID number" area.
Save and the DID was added!