Try setting up on the bird so that they are already in your range before they have line of sight on you. For me, here in the Black Hills, that means you get up above them on a hill or ridge and call down to them. I set up back from the ridge line a bit so that he won't bust me as he comes in...because some of them come in quiet and at oblique angles.
Learn to call softly after you have located the birds, use more of the soft clucks and purrs of feeding birds that are happy and content...those are calls that real turkeys make and few turkey hunters ever learn.