I am selling through VC and generally have good experiences and find it very convenient (if expensive, but I rather not sell in ebay). I am not too sure about their authentification credentials now that they have got so big, but obviously I have had no issues as all I've sold is legit.
I have only bought a couple of things and there I have recently had a bad experience. Bear with me:I bought a YSL College bag with black hardware that was marked as very good condition and advertised as basically new. The seller was professional and thus there was free return for up to 15 days. When I received the bag, the condition was overall perfect only that the black hardware was peeling off in several places! In one of the rings attaching to the bag it was almost completely gone and in others you knew it would get worse from the first use. This is a known problem with YSL black hardware, but none of this was in the description of the bag and the several pics were carefully taken so that the peeling did not show... I was shocked that this had passed their quality controls. On my end as a seller, a couple of times I had something re-qualified by them which was fine, and now they send me a bag with the hardware basically ruined?
So I immediately requested a return. This was within the 15 days but my request made clear I was not making use of the 15-day free return windows, but returning the item as fawlty and not matching the description and condition. This was around Christmas and I was traveling, so I could not send the bag back within those 15 days. When I went to send it shortly afterwards my return documents had disappeared from the site. I contacted them and they said I could not return the bag as the 15 days had passed. I explained that I didn't want a free return, but that the transaction was void as the bag was not in the advertised condition and that I had explained that in my request. They claimed they did not have such request, that it was nowhere to be found. Then they offered that I could sell the bag back in the site and get the full price back (something you can usually do only within a short time frame). I pressed my right to return the item but there was nothing to be done. I made the BIG mistake of paying from my wallet. Never do that, always use Paypal. I would have started a Paypal procedure in that case.
Anyway, I ended up reselling the bag in the site, a very smooth procedure. It sold in seconds. I felt really bad about that, that someone else paid such a high price for a bag that in my view was not worth it. But didn't know what else to do. In the meantime, VC got A 35 eur fee from me for re-selling the bag. Not much, but still...
Then a few days ago I found a copy of my original return request that they refused to acknowledge they had ever received! I had actually taken a pic of it but forgotten (I am very absent minded). I find it incredible that they claim not to keep record of that. So I am again at it with their appalling customer service, to recover my 35 eur more out of principle that anything. And have written a message to whoever may have bought the bag in case they are also not satisfied. But not happy at all about the whole thing and their response.
Anyway I just called their customer service. The lady on the phone was very nice and said they will look into the matter and reply as soon as they know something. She had no clue either why this happened.
