Sorry I am new to this have installed 25.05.3 on to my RUT955 managed after a while to get the router connected to my wifi so I could download the packages "opkg update && opkg install kmod-usb-serial kmod-usb-net kmod-usb-serial-wwan kmod-usb-serial-option kmod-usb-net-qmi-wwan kmod-usb-net-cdc-mbim" but I still can't find a way to control my SIM card any pointers would be much appreciated.
How to "control my SIM card" is only one of the questions that needs to be answered.
See Teltonika RUT955 - modem not detected - #2 by lairsdragon and make sure your modem is powered on and correct SIM slot is selected.
Then show the output of cat /sys/kernel/debug/usb/devices