Unfortunately as part of the Terms and Conditions of Trading in a phone and then wanting it back Samsung say they can't guarantee they can return it and if this becomes the case they'll provide a refund in line what's it's currently worth through the recycle programme @Members_bxaUnyK
Due to length of time you've been waiting this could be the eventual outcome.
From > https://www.samsung.com/uk/trade-in/
" For smartphones and tablets : If you exercise your right to cancel and return the new phone during the 28-day cooling-off period, we will endeavour to return your trade-in phone, but this cannot be guaranteed. In the event the old phone cannot be returned MTR will provide you with a cash equivalent price for the old phone based on the price currently payable for your old phone on the Samsung Recycle website (www.samsungrecycle.co.uk). "
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "