SIM900 + Arduino: AT+CMGL="REC UNREAD" returns 302

Question

I am trying to read SMS messages using SIM900 + Arduino

My code is:

Serial.println("Initializing...");
  delay(1000);
  SIM900.println("AT"); //Handshaking with SIM900
  updateSerial();
  SIM900.println("AT+CPIN?"); 
  updateSerial();
  SIM900.println("AT+IPR?"); 
  updateSerial();
  SIM900.println("AT+CSQ"); //Signal quality test, value range is 0-31 , 31 is the best
  updateSerial();
  SIM900.println("AT+CCID"); //Read SIM information to confirm whether the SIM is plugged
  updateSerial();
  SIM900.println("AT+CREG?"); 
  updateSerial();
  SIM900.println("AT+CPMS=?"); 
  updateSerial();
  SIM900.println("AT+CSCA?"); 
  updateSerial();
  SIM900.println("AT+CSMS=?");
  updateSerial();
  SIM900.println("AT+COPS?"); 
  updateSerial();
  SIM900.println("AT+CFUN?");
  updateSerial();  
  SIM900.println("AT+CMGF=1"); // Configuring TEXT mode
  updateSerial();
  SIM900.println("AT+CNMI=2,2,0,0,0");
  updateSerial();
  SIM900.println("AT+CMGL=\"REC UNREAD\""); 
  updateSerial();

With the following output:

AT

OK
AT+CPIN?

+CPIN: READY

OK
AT+IPR?

+IPR: 0

OK
AT+CSQ

+CSQ: 14,0

OK
AT+CCID

8950201021034280272F

OK
AT+CREG?

+CREG: 2,1,"0115","2CA1"

OK
AT+CPMS=?

+CPMS: ("SM"),("SM"),("SM")

OK
AT+CSCA?

+CSCA: "+50255300222",145

OK
AT+CSMS=?

+CSMS: (0,1)

OK
AT+COPS?

+COPS: 0,0,"Claro GTM"

OK
AT+CFUN?

+CFUN: 1

OK
AT+CMGF=1

OK
AT+CNMI=2,2,0,0,0

OK
AT+CMGL="REC UNREAD"

+CMS ERROR: 302

I think is the CNMI settings or the COPS but I really don't know how to fix it.

Any idea is appreciated.