Hope I can help enough with this; there are a number of caveats...
Ebay isn't very public about this, and their "check the box" method of getting info out of them is circular and very inadequate.
Because of eBay's HIGHLY FLAWED feedback and DSR system, I usually start my quest by contacting the member through the eBay message system but NOT with a formal "not as described" message. I'll contact the member and let them know it wasn't as described first; you'll have plenty opportunity to escalate later. If the seller is smart, he'll realize you're not out to burn him, just wanting the deal you paid for. You'll quickly figure out the nature of your seller, but most sellers are honest and willing to work with you. I say that now, but have to admit things have gotten much worse on eBay over the last couple of years (I've been there 15 years and purchased over 3,000 items)
Rule number 1: Make sure any and all correspondence with your seller is done through the eBay message system! I cannot stress this enough; their customer service people have access to all of it in the system. Forwarding private emails from outside the eBay system won't do any good, and phone calls leave no record also. Take pictures when appropriate and contact the seller. You can attach up to 5 pictures, and I forget how many characters you're limited to, but I have found it not to be enough more than once.
Rule number @: Come across as the good guy, willing to work things out, even if your seller is truly a jack---. I always try to be polite and comprehensive in my discussion(s). Once you have established an exact impass, the easiest way to deal with this is to call eBay. Yes, you can escalate it, but there are a number of "tips and techniques" involved and if you hit a streak of bad sellers--as I recently have--eBay may consider you to be the problem and make matters even worse. They really prefer you do everything in writing, but I HATE typing and often days cannot do it well due to finger issues, so the current magical phone number to call is (866) 540-3229. You're much more likely to get someone in the U.S. if you call during normal U.S. weekday business hours, otherwise the call center you're likely to hit is in the Philippines. Nothing against Philippinoes--I even have friends from there--but their English isn't quite the same as ours as the nuances of United States dialects have been known to create some issues for me.
I could probably write a book on this, but eBay's systems seem to change with regularity. You are welcome to p.m. me and we can set up a phone conversation where I can provide some better detailed info. The main trick to the whole process is to properly lay the ground work first, identifying the discrepancies in a matter that eBay's personnel can understand and verify your complaint. The are also caveats in returning the item to the seller, and there have been instances where I've had to accept the loss instead of potentially setting myself up for even bigger problems--that's happened also...
I know this isn't a complete answer, and it is not eBay's official recommendations either. That said, I've been through the drill enough times to discover what works for me. Hope that helps some.
