Modifying Extensions To modify an existing Extension, follow these steps: Click on either the Extension number or the phone number of the Extension. Modify the details. Click on Save. To modify an existing Extension range, follow these steps: Click on either the Extension range numbers or the phone numbers the Extension range dials. Modify the details. Click on Save. To delete Extensions and Extension ranges, follow these steps: Select the Extension or Extension range using the checkbox to the left of the Extension or Extension range. Click on the Delete Selected