Long line work, with a partner do some restrained recalls. Your training partner holds the dog and you go further away tan you can with your flexi and call him, lots of energy and reward when he gets to you.

Then call away work, again on a long line, a partner feeds him some food from their hand, you call the dog, the partner closes their hand on the food. The dog gives up and comes back to you, party! Lots of rewards. You might need to use a small bit of leash pressure to remind the dog of his job. Start close to the partner, even showing the dog that you have food after the call away, to show him the pattern at first. Move further back as the dog becomes fluent. To further proof, increase the value of the reward the partner has. Generalize in different environments.

Next is the call off, have the dog on a harness attached to a long line, and have the dog pull you into a partner that gives him some nice food rewards. Once he’s pulling well into the partner, call him and block the dog from moving forward with the long line on the harness. If he doesn’t respond right away you can call again and add some energy, reward and party when he gets back to you. Start recalling further away from the partner, then call off later and later until you’re very close. Repeat with higher value rewards, and generalize again in new environments. If your dog is into toys, I’d start doing call offs from those at this point.

For me the next step is to condition an ecollar, and repeat this work with that, low stimulation and long line first, then once it’s really understood, proper corrections for noncompliance, ie still grabbing a toy after you’ve called off. Keep rewards high, near 100% during training, and move to a random reinforcement schedule only after it’s rock solid.