return of item not as listed

[mfcps]

I purchased a 'pastel painting' by Wm Chandler.  The item received is either a photo or litho. some sort of print.  The buyer does not accept that the item is not a pastel.  I offered to keep the frame if the buyer refundedme a portion of the selling price.  Ireceived  nasty reply.  My next step is to have a licensed appraiser give me a written appraisal which will cost me more money.