Confirmation email about returned devices

Hello, 

I have returned the KPN devices on 29th of January via Post. NL point to the following address: "Antwoordnummer 1019 2400VB Aalphen aan de Rijn", that I got from KPN website. Yesterday I received the KPN box more than 14days later to return tbe devices. My question is: Why I do not get a confirmation email, if they received the return devices? To me, that would be the last step for closing the process, that I am missing. Later, I do not want any fine and complain from KPN about returning devices as the process are not complet.

Thank you,