Sending SMS with SIM900

Projects Programming
1

Hi
I'm working on a project with an Arduino Mega and a Sim900 dev board. The idea is to receive a SMS message and reply to the sender. So far I have managed to get the senders phone and store in a string called phone.
The problem is that when I try to use the a compiled command, called cmd, the SIM won't react. With a hardcoded string with exactly the same looks it does work.

void sendSMS() {
  String cmd = "";
  cmd = '"';
  cmd += "AT + CMGS= ";
  cmd += char(92);
  cmd += '"';
  cmd += phone;
  cmd += char(92);
  cmd += '"';
  cmd += '"';
  delay(50);
  Serial3.print("AT+CMGF=1\r");
  delay(100);
  Serial3.println(cmd);                                                      //THIS DOES NOT WORK!
  //Serial3.println("AT + CMGS= \"+46705957262\"");        //THIS WORKS FINE!
  Serial.println(cmd);
  delay(500);
  Serial3.println("Galeaser i Suntak!");
  delay(100);
  Serial3.println((char)26);
  delay(100);
  Serial3.println();
}

Any idea what I miss?