You should be able to return the unopened box if you can find the receipt. Otherwise maybe just donate them to a baby bank? Or there might be a Pampers phone number on the packet to complain?
I exchanged nappies in boots before and it was absolutely fine but I did have the receipt.
I took bk to Tesco and they said to just go and change them to the ones I wanted x
I tried Asda & it was a no x