I have stuffed and frozen Kongs at the ready to give to them to ensure their cooperation for the 30 minutes I'm on the phone. Occasionally a call will last a couple of hours. Believe me, I do everything in my power to prevent long-haul calls, but they happen. For those marathon calls, I pull out the secret weapon - empty peanut butter jars.
I love peanut butter. We go through a lot of it between the dogs and myself. Instead of tossing a jar when it is empty, I save it so the dogs can keep themselves busy licking it clean while I am on those long calls. A bomb could go off in the middle of the room and they wouldn't budge. Well, maybe they would, but they would take their jars with them.