If I am walking a dog that runs off into the bushes I don't call it at all. I remain perfectly silent and keep moving. If I call the dog's name over and over, knowing full well they will ignore me...all it does is let them know exactly where I am, so they can continue to ignore me.... If I remain completely silent, they usually come racing out of the bushes in a panic, looking for me and the other dogs....afraid to be left behind.
I think it's the dog's job to keep his eye on ME...as leader...rather than the other way around.
I don't praise them when they return....I jokingly say, "Keep up or die!"
Of course if the dog responds to a recall...you should ALWAYS praise them.
I just hope that the places you let your dog off-leash are safe areas...not somewhere it could be struck by a vehicle...or get lost.