I have reached out to ATT IoT staff. Their position is that the Quectel modem is configured in THEIR system as supporting VoLTE. I believe this is the problem as the EG06-a VoLTE support is 'optional'. (By the way, this is the same position they took in 2020 when another RUTX11 owner posted on this issue. markhagler sept 29, 2020)