The only "easily defeatable" method that I'm aware of is to make your call from somewhere you don't mind being bombed, make it from a place with multiple egress points, and to stay on the call for at most 90 seconds.
Or put an optical repeater at your target (bombable) site and install a long run of fiber to your safe location, which you then have to abandon. Doesn't seem very practical to me.
Optical repeater? You're overthinking it. You don't need minimal latency or perfect signal quality to make voice calls worthwhile, crap quality is fine. And if you have to abandon a satellite phone because your comms station got blown up...so what? That's just a cost of doing business. They're maybe a couple thousand on the black market, probably the same or less than a MANPAD.
Or put an optical repeater at your target (bombable) site and install a long run of fiber to your safe location, which you then have to abandon. Doesn't seem very practical to me.