Sorry for the Question, but i couldn't find any solution related to this type of modem so,

we have a problem with our spreadtrum modems while we want to send "USSD" by "AT+COMMANDS", some at commands work on this device and some doesn't, After some research we found out, the preferred Network of our devices is always on LTE , and "USSD" is something that works under 2G\3G Networks,

so we decided to change Our preferred Network From LTE to other networks, and check the results again we have "AT^SYSCONFIG" command for that

AT^SYSCONFIG? always returns "17,5,0,2" which means

AT^SYSCONFIG=, ,, Lte prefer, LTE perferred, Not support, CS_PS

and trying to changes this to any other values by AT^SYSCONFIG write command, won't set any thing on device, read command AT^SYSCONFIG? always return "17,5,0,2"

my main question is how to send ussd in such device that seems always to be on LTE mode ?

Thanks in Advance