I have returned my old sky q box but I'm still getting emails saying to return it.
We could usually help you via here by escalating your post to Sky about this but this is not available at present so you will have to contact them yourself so under “Need more help” if it is available should be the number to use:
You can also contact Sky via social media:
https://helpforum.sky.com/t5/Online-Apps-Email/Want-to-private-message-Sky/ba-p/4895295
The process will be a lot quicker if you've kept your proof of posting / tracking information / email from Sky confirming the package was with their courier.
Sky use Unipart to deal with returns and they are taking a number of weeks to process equipment at their warehouse.
Please don’t try to post an image of the Royal Mail tracking or postal receipt as Sky don’t allow them on the forum.