Hello, I'm not a very experienced seller on ebay as I just use it every once and a while and I haven't had this happen before!

Last month I listed a pre-owned sterling silver necklace and a buyer from the UK wanted me to post it there, however I advised them I only post to the PayPal address listed on their account (theirs was in AUS and I only post to AUS anyway).  I had listed many photos of the item showing all sides of it, as many as possible, and had described the necklace as pre-owned but in good condition (it's sterling silver and was a bit tarnished that's all but I wouldn't say it was bad condition).    

I posted this at the beginning of October to an Australian address which should take 5-7 business days.  In the middle of October, I left for Africa meaning I was out of internet connection, however I gave enough time for the buyer to receive their item to the Australian address and contact me with any issues before I left and then I could reply to rectify any issues. 

On the 25th October (while I was in Africa) I received an email from the buyer stating "I received the necklace from Australia to the UK but the silver metal is marked and discoloured in alot of places on front and back.I request a partial refund so I can get it professionally cleaned".  

I was still in Africa and thus couldnt check or reply to this.  On the 30th October, I received a message from Ebay stating they had opened a case as I had not replied and the Ebay email said 'We've thoroughly investigated the case and found that the buyer should return the item to you because it’s not as described in the listing'.

However I got back from Africa yesterday and today is the cut off date for me to finalise this case otherwise it will be deemed in the buyers favour..

Can someone advise me what to do in this situation?

Can I make a counter case as I believe the item was exactly as described as per pictures and description?  

Does this mean that sterling silver needs to be professionally cleaned by a seller before we post it haha I'll post a link about how sterling silver naturally tarnishes all the time http://www.ebay.com.au/gds/Will-sterling-silver-tarnish-or-will-silver-turn-my-finger-green-/1000000...

The buyer is also wanting a partial refund to get it cleaned, which I don't agree with (it only needs a silver cloth.. ) and it seems that they are now asking to send the item back (since the buyer has posted it onwards to the UK whereas I only posted it to an address in Australia) is that allowed?