Customer claiming item not as described

[bebebaubles]

A customer claims a Wok he bought was not as described and has a huge scratch.  My husband and I got the Wok as a gift, never used it and both looked at it and packed it together.  What do you do when this happens?  We are going to be charged almost $40 for the shipping and get a Wok back with a scratch

So here is the other weird thing, we also sold a Crock Pot the same day March 21st and that person wants to return also.  Both sold Mar 21st, both buyers are an eight in feedback, both were delivered on Mar 25th and both buyers contacted us Mar 30th about the return, five days after being delivered.  Delivered to two different states. 

We have been selling on Ebay for over 15 years, is there anything we can do and how do you prevent this from happening?