What latest approved FW we have for EM73xx product can be found here::
https://source.sierrawireless.com/resources/airprime/software/airprime-em73xx_mc73xx-fw-package-latest-release/
Voice is supported per product/certification approval, voice enabled/disabled setting can be queried via the AT!custom? command setting:
• “ISVOICEN”—Enable/disable voice functionality.
:
• 0 = Disable voice
• 1 = Enable voice
Please see AT command guide for details:
https://source.sierrawireless.com/resources/airprime/software/airprime-em73xx_mc73xx-at-command-reference/