Question
CCP v1 does not provide the opportunity to add/reduce Backup Diskspace despite the resource the upsellable.
Behavior of CCP v2 is OK.
Cause
Software issue #CCU-17638 does not allow to upsell the resource if its minimum included amount is 0.
Workaround
Configure Service Plan to that included amount of Backup Diskspace resource is more than 0.