My service provider lets me download messages as audio files.

I’d download them and pop them into a player that can display waveforms, so that you can skip those pocket dials with a bunch of silence. Or so that you can speed up the audio to 1.5x, which will be 33% faster than listening at normal speed.

OR if you dont feel like working for a few days, play the stuff back at 0.75x for a 33% increase of your billable hours.