This simple code can be use to send a text message and make a voice call using AI Thinker A6 GSM/GPRS Module.

A6_test.ino

#include <SoftwareSerial.h>

SoftwareSerial A6Module(10, 11); //RX,TX
char input='\0';

void setup() {
  A6Module.begin(115200);
  Serial.begin(9600);
  delay(500);

}

void loop()
{
  if (Serial.available() > 0) {
    input = Serial.read();
  }
  if (input == 't') {
    sendMSM();
    input = '\0';
  } else if (input == 'c') {
    makeCall();
    input = '\0';
  }

}

void sendMSM() {
  A6Module.println("AT+CMGF=1");
  delay(2000);
  A6Module.print("AT+CMGS=\"94710000000");
  A6Module.print(char(34));  // "
  A6Module.print(char(13));  // CR
  A6Module.print('\r');  // hex equivalent of newline
  delay(2000);
  A6Module.print("A6 test message");
  delay(500);
  A6Module.println (char(26));  //ctrl_z

}

void makeCall() {
  A6Module.println("ATD+94710000000");
  delay(20000);
  A6Module.println("ATH");  //end call

}