I have a problem about using AT command. I am trying to send AT+CUSD command using C#. The problem is when I submit AT+CUSD command, the GSM returns OK with NO +CUSD reply. This is for both in my C# app and Terminal.
For example, I submit the first line and GSM returns the second line:
In the starting, I send these commands to initialize GSM.
Do I miss something? Please help.