Sending USSD command to a modem Mobile broadband on linux without stopping the current ppp0 command

kilog

Hello friends

I am running wvdial (ppp0) on a modem (/dev/ttyACM0) Mobile broadband on linux to supply internet to a small group of users.

I want to use USSD command to catch the balance of the current 3G internet connection
But for now the only solution that I have is to:
1- stop the wvdial (and ppp0) command in order to free the /dev/ttyACM0 device and then
2- send the USSD through the /dev/ttyACM0 device
3- relaunch the wvdial to run the ppp0 internet link again
By doing that the users connected on that internet link are disconnected, which is the problem that I want to avoid.

So my question is how can I send USSD (and later SMS) to the same modem without stopping the current ppp0 link on the same modem

Best regards