I ordered 20 FAL mags "used but in excellent shape" from Sportsman's Guide. Good ones like true NIB Austrian and IMI mags started getting impossible to find about eight years ago. They sent me a box of rust, I mean rusted inside and out and parts literally falling off the mags. Some were rusted together in blocks of four or five. Another company did much the same, Cheaper than Diamonds? Then AIM Surplus tried to trick me with Korean mags sold as Austrian; a guy at a gunshow tried the same thing face to face. In the wrapper, it's hard to tell at first. Each time they tried to put me through the wringer, saying "they were inspected prior to shipping" and all the usual shit. FWIW, a real Austrian FAL is a pretty nice battle rifle and feeds like a champ with Austrian or IMI mags, but fakes and junk are it's Achille's heel.
So I sent their box of rust back and did a chargeback on the card for services not rendered, and I pitched a fit at the gunshow and made a scene and the guy gave me my money back, reluctantly. AIM Surplus I accused of bait and switch. In each case, I sent the garbage back ASAP and got the CC company to charge back ASAP. NEVER had a problem doing that thus far, unfortunately had to do it a few times. Just document everything well, just in case.
I don't tolerate bait and switch, lies, fucked up orders, etc., and I don't pay to ship them back either. If you send me garbage, I'll be getting my money back, it's the whole point of a CC for online purchases, but if you want your garbage back you're gonna have to email me shipping labels or else you can make an appointment and pick it up in person whenever you happend to be in the neighborhood.
Oh, on certain orders, especially used items, I always email and have them describe explicitly what I should be getting. So an email saying I'm getting good parts and I get a box of rust? Well, that doesn't fare too well for them if they wanna dispute my claim. I take pictures of the junk before I send it back too.
Ebay has a pretty good service when it comes to returns too, at least on paper. I've never had to use it, but it's why I never use F&F unless I'm literally giving the money away with no strings attached (like donations, etc.).
High end companies and companies that stand behind their shit aren't usually a problem though. I bought an ACOG off Ebay cheap that had a cracked prism and some other issues and they fixed it and had it back to me the same week. Like new. I have several stories like this. It's those companies I tend to stick with over time.