MacPalace.com MACPalace, Inc I ordered a specific high end part and they supplied a low end part. California

I ordered a Logic Board from this company. I paid for a high spec board but they sent me a low spec board.
I purchased a Logic Board for an iMac 27 inch3.4GHz on January 5 2018 as below.
820-3299 MD095LL MD096LL A1419 Manufacturer Part Number: 661-7160
Cost US$406
Shipping: USPS US$109.07
The website is MacPalace.com
The web page stated there was a 60day warranty included.
The order number was 45797.
The shipping was stated as 6-10 days.
I received an email to the effect that the part had been shipped on January 24 2018, 19 days later.
I finally received the part on February 1 2018.
After installing the board I discovered that they had in fact shipped me a cheaper board.
The board I received was for a model which had only 512MB VRAM instead of the 2048MB VRAM the specified board should have had. They had sent me part number 661-7156.
I complained about this by email. They, at first, claimed that they had never specified the video card. I pointed out that it was tantamount to false advertising to supply a different part to that advertised. They claim to have supplied a "compatible part".
Finally they said they would give a refund if I sent the part back (being unable to supply the correct part I suspect!).
I duly mailed the part back (at my expense!) from Australia.
My postal service informed me the board was delivered back to them on February 12 2018.
I have sent many email reminders to them requesting my refund, but have had no response.
I have reported them to BBB of Los Angeles to no effect whatsoever.