Earlier quoted context omitted.
Find the telematic's antenna, and put a 50ohm resistor across it. It can scream into it's own private void.
It seems like this is not enough: https://www.tacomaworld.com/threads/simpler-solution-for-dis... The most reliable way to permanently silence the cellular modem is to pull the relevant fuse. In the above case, this also disables the microphone, which I think is a positive. Unplugging the DCM entirely, however, seems to disable to right speaker, which is wired through the DCM for some reason.
(Yeah, technically horrible but I’m sure someone will find a way)