Depending on how much you invested in the musical instrument and the result of your contact with your credit card company, you could have the cease and desist letter, and the terms of sale offered on the website, reviewed by an attorney in your area.
If the site is a legitimate one, it should have contact beyond website and email contact. Although a company that offers only a PO Box is one best avoided, it does not necessarily mean the company is not legitimate - although it should give any buyer pause. You can send a letter to the PO Box, though, detailing your complaints with the item and how you would like the matter resolved. Let the company know that you intend to send the musical instrument back and stop payment on the item but you need further contact information in order to complete the process. See what happens.
Are you an experienced purchaser of musical instruments that are collector's items? An "excellent" condition is different for collector's items. Collector's items do not necessarily have to work or be in pristine shape, in other words. A past history of the item or a signature on the item can bring an "excellent condition" statement and the item can have a higher value than the same item that works and is pretty but does not have the same history or a signature. In fact, sometimes the defects are what makes it valuable.
I was planning on having the issue reviewed by an attorney. The ex-musician who owns the site has maintained his name/contact# a secret from the start and has said so for "obvious" reasons. Sending a letter to the po box will not get much more done. I have sent countless emails outlining my complaint. They have always come back with an excuse and/or buyer's remorse. It's actually not a musical instrument...it's the case it was supposed to fit into. (the guitar is also questionable but I don't see me finding another like it for some time so I told them I can live with it) The case was supposed to be in excellent condition and fit the guitar snug.
I've been doing research on this guitar for over 30 years. The case was a last minute thing. I offered to send them a brand new case to put it in but they came back with the case I purchased. They showed 2 photos of the case. Open and closed...that's it. When they said it was in excellent shape I didn't see the need for more pictures. I trusted them. Like I said, the guitar is good but not pristine, but the case does not hold the guitar snug, nor is it in excellent condition.
I'm trying to hold myself back from releasing too much info for fear of them doing something else. they offer a 14 day return on their ebay site/store but threatened me when I brought this up. It was public info but they are claiming I'm stalking them.
The guitar case was misrepresented and all I want is a discount or a full refund. They are ignoring me and now accusing me of harassment when I fell I am in the right.