Digital Voice trhough modem FX

IoT Gateways Legacy FX/FXT series
1

I need send the digital audio throught serial modem FX.
I start voice call with at command, after i need send the digital audio through serial.

Can I help me ?

2

https://forum.sierrawireless.com/t/what-modems-are-support-the-at-command-of-activate-voice/7202/4

https://forum.sierrawireless.com/t/fx100-audio-transmission-via-usb/7098/1

3

Thank you for information.

Can I change the firmware for the model Fastrack Xtend HSPA for send voice trought serial port ?