Modest sample size, so take with a grain of salt, but I've found that sometimes at busy periods I've had better luck calling the hotel using a googled public number on my cell phone than actually using the in-room phone. Also sometimes the mapping of the hot keys on the in-room phone (e.g. front desk, room service) gets messed up and so it just goes nowhere or rings forever. And then there are course the cordless in-room phones which I have never been intelligent enough to figure out how to use (my workaround is to put it on speaker...).