Android Sending Group SMS

static List<String> phone_num = new ArrayList<String>();
static List<String> SMS = new ArrayList<String>();

   @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
            readExcelFile(this, "/sdcard/Excel.xls");
    View readExcelButton = findViewById(R.id.buttonSend);
            readExcelButton.setOnClickListener(this);

}


      public void onClick(View v) {
        switch (v.getId()) {
        case R.id.buttonSend:
          for(int i=0;i<phone_num.size();i++)
            {
               SmsManager smsManager = SmsManager.getDefault();
               smsManager.sendTextMessage(phone_num.get(i),SMS.get(i), null, null);        
                }

  Toast.makeText(getBaseContext(), "Sendingfinished",Toast.LENGTH_SHORT).show();  


                break;
       default: break;
        }
    }