Why on earth would you be streaming 320kbps? Roughly telephone-equivalent bitrate is <100kbps, potentially down to 8kbps or so for (bad) speech. Noise-gating

Why on earth would you be streaming 320kbps? Roughly telephone-equivalent bitrate is <100kbps, potentially down to 8kbps or so for (bad) speech. Noise-gating or even rudimentary voice detection (sound is a voice, not random ambient) can reduce that duty cycle to a tiny fraction. So you could get a lot of useful information out for <100MB/day. If you wanted to be sneaky, there are probably viable ways of hiding it from casual detection; buffering locally and appending to user-uploads (images, video, voice) when there's already data flowing. Or do some pre-processing on the device to slim it down even more. Maybe only when it's on external charge to avoid running the battery down too far. I'm not suggesting this is actually happening, but it's far more plausible than your estimates suggest.