AT+CMGF? Command Does Not Work

I have a project with Sixfab NB IoT EVB and it has BC95-B20 Quectel. I try to use AT commands. When i write AT then its OK. But when i write AT+CMGF=? then the response is ERROR. What is the solution. I checked the ethernet bu i did not found anything. Can somebody help me, urgently?

Hi Elif
AT+CMGF does not support this instruction

What features do you need to test?