Jonsered CC16i battery-powered string trimmer head replacement

I own a Jonsered CC16i battery-powered string trimmer.  There doesn't seem to be a mechanism to stop the (P25) trimmer head from turning so you can replace it with a new head or brush cutter blade.
 
No holes evident in top view, side view, or bottom view. The only potential method is to pop off the spring-loaded feed bumper, which exposes a slotted screw/stud (presumably the one that connects to the motor).  I've tried to loosen the head by holding the head firmly and attempting to twist it while a screw driver is inserted in the slot, but it doesn't want to budge and I don't want to break it.
 
Is there another way?
 
FWIW, I've posted a youtube video at

Yes, it's reverse threaded.  I want to spin the head off in a clockwise direction to remove the entire assembly. However, the head doesn't seem to want to budge when I insert a screwdriver and apply torque to the P25 plastic housing (regardless of direction).
 
The manual shows how to install the head but does not provide details on preventing the head from turning (i.e., no hole as is typically found on many other trimmers).

@sRTsFZ6:  Thanks for your response; unfortunately, while the diagram from page 10 shows how to remove the top of the P25 trimmer head (to replace the trimmer line), it doesn't provide information on removal of the entire trimmer head (which is depicted in the inset of the diagram above). Continuing with the diagram, if I could prevent the head from turning, and use the left hand (shown above) in a clockwise direction I could spin off the head. I haven't found a way to keep the head from turning relative to the trimmer shaft.