Phones connect and handshake with the local cell at different levels of power. Initially, they connect at low power, if they do not receive a signal, they increase the power until they get a better signal.
This is why your mobile battery discharges faster in a poor signal area.
On board, the airborne system receives at the lowest power setting, hence no threat to the systems.
I call Maintrol, Ops, the Wife, the Lover etc etc while taxiiing in.
Providing it is safe to do so and in a hands free environment, while not endangering any deer dolphins or puppies 