If I'm reading your first post correctly, it sounds like you did have 10 hours rest.
5:45 original report minus 9 hours is 20:45. The new report of 7:45 is then 11 hours from 20:45.
The way I understand it, if you were in rest when the company called you to notify you of the change, that interrupted your rest and you need 10 hours rest from that time before any assignment.