How To Send Back Superonline Modem!

I cancelled my Superonline fiber broadband subscription yesterday for the service with number 110196937716. Right after the cancellation, my internet connection was cut off the same day, but I was informed that I have to wait for an SMS or a phone call to be able to return the modem. I am leaving the country this Wednesday and I clearly stated that I cannot wait indefinitely for this message or call. I want to return the modem today or tomorrow at the latest, in a clear and simple way such as dropping it off at a Superonline/Turkcell store or any other address or courier option you provide immediately. I do not want to face any extra fees, penalties, or issues later just because I could not wait for your SMS or call while I was already abroad, especially since the service has already been stopped. I request that you urgently provide me with an immediate and practical solution for returning the modem before I leave the country, and that you confirm there will be no additional charges or problems related to the modem after I hand it over.