Q: Who do I contact to manage usage on IPad l ? When I try to downgrade it doesn't respond to "done" .

Hello John,

Thank you for using Apple Support Communities. 

The most likely reason for not being able to click the "done" button is that you have missed a particular step. Take a look at the section "Downgrade your icloud storage plan" and make sure you have hit all the steps. 

From that article referencing iOS:

iOS:

If you're using iOS 8, go to Settings > iCloud > Storage. If you're using an earlier version of iOS, go to Settings > iCloud > Storage & Backup.

Tap Change Storage Plan.

Tap Downgrade Options and enter your Apple ID password.

Choose a different plan to use when your current storage plan expires.

Tap Done.

iCloud storage upgrades and downgrades - Apple Support

Regards,
Jeff D. 

Hi John,

Since this hasn't resolved your issue, you may find more information by using another one of Apple's support resources - https://getsupport.apple.com/GetproductgroupList.action.

Regards,
Jeff D.