Depending on how the storage is used, managed, it may appear as available.
And you may need to institute a management scheme to remove items you've
saved to storage (in cloud and in device) in order to best use capacities there.
iCloud: Delete photos and videos to save storage
Manage your iCloud storage - Apple Support
If you reach or exceed your iCloud storage ... delete files you store in
iCloud Drive from your iPhone ... is set up to access iCloud ...
https://support.apple.com/en-us/HT204247
... in iCloud and access them from your iPhone or ... upgrade your storage
— up to 2TB. And now you can share a 200GB or 2TB iCloud storage plan ...
iCloud Drive FAQ - Apple Support
iCloud Drive lets you securely access all of your documents from your iPhone
... You can use that storage space for iCloud Backup, ... iCloud Drive FAQ.
https://support.apple.com/en-us/HT201104
While these linked support sites have clues, because you've not stated how
or what you have tried (in detail) in attempt to access or manage storage,
there is no definitive advice one could give; short of troubleshooting your side.
In the Settings, iOS allows you to control usage and in a reverse logic way, to
manipulate the contents in a way so as to manage the usefulness of the total.
The answers may be in the iCloud information because this allows one to share
across most all iOS and macOS products, with your Apple ID & iCloud.
{Note the internal storage within an iOS device or your Mac, isn't what appears
in your purchased totals that you buy. One is on the Cloud, the other is local.}
For information about managing storage space on your devices, see:
- Check the storage on your iPhone, iPad, and iPod touch
- Free up storage space on your Mac
- About storage on your device and in iCloud
- Manage your photo and video storage
- If you need more space for an iOS update
Sorry to not be more detailed or specific.
Good luck & happy trails! 🙂