Oh, ok.. so you are talking about the review queue. So you are saying that you flag (that’s what you mean by report, I think) topics that are in the wrong category. Then you decide on the action you want to take on the flag.
In this case you made a mistake and took an action that you did not intend, and you want to change your mind and take a different action?
Have I got that right now?
If so then yes, it is not possible to flag the same post again after action has been taken. As moderator why don’t you just move the topic yourself?