Sofort Payment Gateway

Hello,

I have a small issue, I hope you can help me with it.

I’m using Sofort Payment Gateway plugin for my shop. The plugin is made by WooCommerce.
https://docs.woocommerce.com/document/sofort-com-gateway/?_ga=1.206236826.842121469.1491392708

I would like to change the transaction reason to be: P4360-043-015. In the plugin documentation, they mentioned an example for the filter that I can use and add to function.php file in the child theme to change the reason. But actually, I don’t know where I should add my new reason in this code.

This is the code:
function filter_my_transaction_reason( $message, $order_id, $order_number ){
return sprintf( ‘My Order %s’, $order_number );
}
add_filter( ‘woogate_sofort_transaction_reason_1’, ‘filter_my_transaction_reason’, 10, 3 );

I tried to contact with the Woocommerce support but they are totally helpless.

I hope you can help me with this and I will be thankful.
Thank you so much in advance.

Ammar