Deleting a volume is something you should take into deep consideration before doing so. Once you delete a volume you cannot get your files back. We recomend you get a storage device to hold your files before deleting your volume.
On "Your Volumes" page where your volumes are listed there is a button labeled "DEACTIVATE VOLUME", when you click on this you will be asked for further confirmation. After clicking "ok" a request to deactivate your volume will be made.
If the deactivation request is successful the icon beside the volume name will turn red, on the right side there will be a count down until the volume is fully deleted. You may be charged for the volume while it is deactivated but this will stop after it is fully deleted.
After deactivating a volume you will be given 30 days to download your files, you will not be able to upload or replace any files during this time.