Going from the Samsung Faqs page here > https://www.samsung.com/uk/shop-faq/returns-and-cancellations/ one of the relevant faqs states " We will notify you of your refund via e-mail within a reasonable period of time, usually within five to ten working days of receiving your return, and refunds are made to the same payment method you used for purchase. "
I would also factor in the time of year and how busy both DPD and Samsung Returns will be.
Unfortunately if Samsung are saying they haven't received the parcel then they are going to have to investigate this with DPD's internal support team which is reasonable, however this shouldn't on the flip side inconvenience the customer unreasonably.
I also had some issues with a return and found putting this in writing via email created a paper trail and pushed the refund forward.
e : email@example.com
I wish you all the best with this.
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. "