Hello Gordon Shamway,
Are the deleted messages still within the Recently Deleted section of the Messages app?
If so, you may try deleting them from that Recently Deleted area of the app, and see if this has helped out.
On macOS you may use the following steps to find it:
- Open the Messages app
- Select the View menu (at the top of the screen)
- Choose Recently Deleted in the list.
- Select the conversations on the left, and click the Delete button on the middle section.
The messages should automatically delete themselves permanently from the Recently Deleted section after a 30 day span as well.
This page can also provide some further help with managing iCloud storage: Manage your iCloud storage - Apple Support
Cheers.