hey dude chcek these one

[rupa]

void setup(){

Serial.begin(9600);

delay(200);

}

void loop()

{

Serial.println("AT");

delay(1000);

Serial.println("AT+CMGF=1");

delay(100);

Serial.println("AT+CMGS="+9779804495672"r");

delay(1000);

Serial.println("sms from arduino");

delay(100);

Serial.println(char(26));

delay(1000);

 

}

 

 

here is it simcom900a need external 12 volts supply after giving supply press the power button until u can seen  led with blue light blinks it means ur sim is working connect tx to tx and rx to rx pins of arduino and check it