modem didn't respond to AT commends

Question

I want to perform some AT commends on my huawei ec122 modem (locked) but i didn't receive any response from it. i am using c# to perform request with waterline method the port open without problem and my request are send successfully. i know that because i installed wireshark and i guaranteed that my request are send to the correct COM port that modem original application communicate with.

port = new SerialPort("COM13");  
port.Open();
port.WriteLine("AT");           //Get the modem's attention
port.WriteLine("ATI");          // Get All Manufacturer Info
port.WriteLine("AT+CGMM");      // Get USB Model
port.WriteLine("AT+CGMI");      // Manufacturer
port.WriteLine("AT+CIMI");      // Get SIM IMSI number
port.WriteLine("AT+CGSN");      //Get modem IMEI
port.WriteLine("AT+CGMR");  

i didn't post this on stack because i don't think it have something to do with code, i suspect that it have to do with the modem been locked, and i need to guaranteed that. what do you suggest for me to do ? thanks.