Have you contacted the seller? Or maybe sellers if you ordered from one but the parcel you received is from another. A seller would want to know because they have to send messages of apology to you and the other buyer.
If you file a Not As Described claim for a GSP item usually you don't have to return it and you get a full refund when it is a GSP mistake. But you still want your item and so does the other buyer.
Users here have gotten in trouble for posting phone numbers but maybe you could Google "Pitney Bowes phone number" and see if that helps.
This is not the first time this has happened and I think in the other case the 2 buyers just mailed each other their parcels but if I can find another case I will post it and any info.
First let the seller(s) know whats going on.