A number cannot be released while something on your account still depends on it. This is deliberate — releasing a number that is still doing a job is how businesses accidentally take their own phone system down.
When you start a release, we check for everything attached to the number and show you the list. You need to detach each item before you can continue.
What can hold a number
It is your account's main number
The main number identifies your account on outbound calls and account records. Choose a different main number first, then come back and release this one.
An extension is bound to it
The number rings a specific extension. Unbind it under Extensions, or point the extension at a different number.
A ring group or call queue uses it
The number is an entry point to a group or queue. Remove it from that group or queue's configuration.
A voice menu points at it
An auto-attendant or menu option routes to this number. Edit the menu and change the destination.
An AI receptionist answers on it
The number is assigned to a receptionist. Unassign it under the receptionist's settings.
A fax mailbox uses it
The number receives faxes. Remove it from the mailbox, or release the mailbox first.
It has an active emergency (911) registration
The number has a registered emergency address. This one matters most: releasing it would remove a working 911 path. Deactivate the registration under the number's emergency settings once you are certain the number is genuinely going away.
After you have cleared everything
Start the release again. The check re-runs, and if the list is empty you move on to the billing step.
The number is still blocked and I cannot see why
The list shown to you is generated fresh each time. If it keeps showing something you believe you removed, the change may not have saved — reload the page and check the item directly. If it persists, contact support with the number and the item name.
Trying to reorganise rather than cancel? You do not need to release a number to change where it rings. Adjust its routing under Phone Numbers → Your Numbers instead.