invoice for microstation

Good day

Recently we have purchased an update of 6 licenses for microstation powerdraft, including an open access license subscription.We have 11 workstations, 5 with new version and 6 with old version.
The workstations on which the 5 new versions are installed also have the old version.
For the month of August we received an invoice for the use of 5 licenses.In the Monthly usage by user report, I see users who no longer work with checkouts.
Where is the error?and we still have the possibility to cancel the invoice for non-use.

Thanks in advance.