Are you checking the cellular bands, or just your local 802.{3,11}? SoC exist with builtin LTE/CDMA/etc.

edit:

Also, voice compresses really well if you don't care about the quality. With a codec that uses <10 kbit/s (e.g. GSM-HR, AMR), the storage requirements are at most 2.4 MB/hour. A simple gate filter that cuts out quiet periods should cut the storage requirements down to only a few MB/week. A typical flash chip used to store the firmware could easily store years worth of typical household speech in the non-firmware space.