Intent callIntent = new Intent(Intent.ACTION_CALL);
String encodedHash = Uri.encode("#");
String ussd = encodedHash + "06" + encodedHash;
startActivityForResult(new Intent("android.intent.action.CALL",
Uri.parse("tel:" + ussd)), 1);
and give this permission in android menifest
<uses-permission android:name="android.permission.CALL_PHONE" />