Cancelled but still charged for monthly homespot?

I have cancelled my O2 HomeSpot since last month, but I have not returned the HomeSpot device, since I don’t know to which address I should return it. I should not get a Rechnung for the Tarif, since I did not use said router or its services. Where should I return the device?

Edit o2_Antje: Moved from o2 Home to English Community / 23.01.2025 / 19:50 Uhr