[mothered]

The wrong item received? Wont they ask for it back?

Yes they will, hence you'd need to purchase a very cheap Item on a different account from the same company of equal weight to the original Item.

When they request the return, send that. They'll scan It and see that It's part of their Inventory, hence assume It was Incorrectly dispatched.

Do you mind expanding on the sealed box method?

In short, replace the original Item with anything of equal weight and reseal the box without any signs of tampering whatsoever.

When they receive the return, they'll assume It hasn't been touched, place It back Into stock and Issue a refund thereafter. That's a basic elaboration - refer to my blog for an In depth guide on this and any other method, the wrong Item received Included.