Good day. Thank you for your question.
To change the server settings, the SMS commands are as follows:
With username and password : <username><space><password><space>setparam 2004:your domain;2005:your port;2006:0
Without username and password : <space><space>setparam 2004:your domain;2005:your port;2006:0
Kindly take note that if you are sending it via GPRS then there is no need for username, password or <space>
You may refer here for the list of SMS/GPRS commands - https://wiki.teltonika-gps.com/view/FMB_SMS/GPRS_Commands
You may refer here for the Parameter List - https://wiki.teltonika-gps.com/view/Template:FMB_Device_Family_Parameter_list
Kindly go through this and let me know if it helps.