Issue
When you delete an instance while the volume is attached, sometimes you can’t operate the volume. For example, you can’t delete or attach the volume to another instance.
In this case, The instance is deleted completely, but the volume attached to “None” and status is still “In-use”.
Solution
In order to avoid this issue, please detach a volume after turning off an instance before you delete an instance.
If this issue is happen and you can’t operate the volume, please inquire with a ticket.