How to shoot AT commands on sim in OpenWrt

I am using the QMI protocol for the LTE network. In /dev/cdc-wdm0 is available.
Can anyone tell how to shoot AT command for the /dev/cdc-wdm0

In general your modem has an tty port for AT commands, independantly of the QMI port.
On my case (MC7455), the modem has /dev/cdc-wdm0 for QMI and /dev/ttyUSB2 for AT commands.
the driver for usb/serial needs to be loaded to expose this port

If you just want to send basic SIM commands, you can also use libqmi/qmicli which is only based on the QMI port ( /dev/cdc-wdm0).
Look at qmicli --help_uim