The end user (Plesk client) wants to cancel 200MB extra space he purchased in the past. In his /cp there is no option to downgrade the diskspace.
"Show in CP" is disabled for the
"Disk space quota" resource in the hosting plan.
The solution here will be to Enable
"Show in CP" option for
"Disk space quota" resource in the hosting plan, upgrade the subscription to the latest version of the hosting plan at
Top > Billing Director > Product Manager > Hosting Plans > <some HP name> > "Subscriptions" tab > Upgrade Subscriptions