How to delete and recreate an extension?
Deleting an extension is permanent and will delete all voicemail messages and faxes in this extension's mailbox. If you are changing a person's extension number, we recommend that you first create his or her new extension and forward all voicemail messages and faxes from this extension to the new extension. Then also consider if there is a phone currently registered to this extension. You want to unconfigure that phone first, then you can delete this extension.
To delete and recreate an extension
First create new or replacement extension
Forward all voicemail messages and faxes to new extension
Unconfigure currently registered phones
To unconfigure a Digium phones
Go to Setup → Phones → Digium Phones
View Assigned phones and Extensions
Unassign
You will be asked to verify :"Are you sure you want to remove this phone assignment?" Click Yes, Remove Assignment.
To unconfigure a Phone Feature Pack supported phone
Go to Setup → Phones → Phone Feature Packs
Click on the Configured Phones tab
Locate and check the mac address of the phone
Click on Unconfigure Checked Phones
Delete extension
Go to Setup→ Extensions → Manage
Locate extension and Click on Delete
You will be asked to archive voicemail and faxes. To archive the voicemail \
messages and faxes for this extension, click "Download Voicemail/Fax Archive"
Then click "Yes, Delete Extension".