Mute the taxi driver. That's it. Just mute him.
There is no configuration for this addon.
The addon uses the master dialog volume controller in order to mute the taxi driver. If you are logged out by Carbine or manually log out/switch characters while on the taxi the original volume will be saved. If, however, the game crashes for whatever reason then Carbine will not save off the original volume and master dialog volume will be left at zero. There is no way through the API to overcome this at this point in time.
See Shut the bleep up for muting the Holocrypt.