If the item is not as descrbied and the seller sends you a return label then that is where you send it too.
Was it the seller or ebay who sent the returns address
You need to do returns through the Resolution centre.
Open a not as described dispute at the bottom of the page under Resolution Centre and escalate it after another 8 days
The seller needs to send a pre paid label for the return
If they dont then ebay should when you escalate the dispute
Make sure it goes back tracked and that the tracking is in the dispute
You have 30 days from the day of delivery to open a dispute in ebay
Ebay money back guarantee
http://pages.ebay.co.uk/ebay-money-back-guarantee/
