For making a call activity using intents, you should request the proper permissions.
For that you include uses permissions in AndroidManifest.xml file.
<uses-permission android:name="android.permission.CALL_PHONE" />
Then include the following code in your activity
if (ActivityCompat.checkSelfPermission(mActivity,
Manifest.permission.CALL_PHONE) == PackageManager.PERMISSION_GRANTED) {
//Creating intents for making a call
Intent callIntent = new Intent(Intent.ACTION_CALL);
callIntent.setData(Uri.parse("tel:123456789"));
mActivity.startActivity(callIntent);
}else{
Toast.makeText(mActivity, "You don't assign permission.", Toast.LENGTH_SHORT).show();
}