API response fetching method not called CI - php

Question

I have bad english, but i hope I can explain you my situation.
I have payment controller and two methods.
class payment extends MX_Controller{
public function __construct(){
parent::__construct();
$this->load->model(get_class($this) . "_model", "model");
}
public function pay(){
//Gets form data and sends to payment service
}
public function check(){
//Gets response from payment service and acts according payment
//status
}
}
First sends data to payment service and second have to do something according payment response scenario.
So in my payment cpanel I wrote this url "htts://my-domain.do/payment/check" for response.
The first method works successfully, it sends all needed data, but my second "check()" method does not called.
When I simply write https://my-domain/payment/check it still not working, but when I call like this https://my-domain/index.php/payment/check it works.
My .htaccess also configured.
I use CI 3. Is there any one who had the problem like this.
My .htaccess file look like
RewriteEngine On
Options +FollowSymLinks
Options -Indexes
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteRule . index.php [L,QSA]
And in app/config/config.php
$config['index_page'] = '';