Changed a few things.
void setup(){
Serial.begin(9600);
delay(1);
Serial.println("AT");
delay(1);
Serial.println("AT+CMGF=1");
delay(1);
}
void loop(){
delay(1);
Serial.print("AT+CMGS=");
Serial.print(char(34));
Serial.print("9406686543");
Serial.println(char(34));
delay(1);
Serial.println("This is a sms fromxxx....... just saying hello....");
delay(1);
Serial.println(char(26));
while(1);
}
And got this.
AT
AT+CMGF=1
AT+CMGS="9406686543"
This is a sms fromxxx....... just saying hello....
Like AWOL mentioned, 34 is a quote,
Serial.print(char(34));
Serial.print("9406686543");
Serial.println(char(34));
The code above can simply be written as
Serial.print("\"9406686543\"");