CBS has a rule that one could only hope that the other networks and cable stations would follow. 

Because it is TV and not radio, CBS will not let Presidential candidates join their shows via phone. It's on camera or no go. 

That is exactly what happened this morning on CBS This Morning. Donald Trump was scheduled to appear, but he could not make it on camera. Trump wanted to phone it in, but CBS EP Chris Licht would not allow it and bumped Trump.

It is nice to see that some networks will not pander to Trump's every want and need (I'm looking at you CNN, MSNBC).

Props to Licht and CBS for standing their ground. 

To be honest, we don't know how Trump can dial the phone with those tiny fingers to begin with. He must have a handler make the call.