I will share a couple things that help me.
When all else fails, do any of the following once, short and as loud as possible. Blow as hard as you can through any call, short and loud. If you are close to your truck, slam the door or honk your horn. Give them what they haven't heard and give it to them loud, that will sometimes work when nothing else does.
But honestly, you will kill more birds by watching them and learning where they like to feed and their daily routine. Turkeys have rounds that they make every day unless you upset their routine. From the time they wake up until they go back to the roost, they will repeat that routine most of the time unless disturbed, turkeys are very predictable and we kill the dickens out of them all season long because of that weakness.
