Man guys and gals, I feel really bad for you, so please do not take this the wrong way...and it's not directed at you. But when Big Value popped into the scene here on POTN a few months ago, I was super skeptical. I did a couple of hours of research and found out that they are a descendent of the infamous Broadway Photo. For those that are unaware, Broadway Photo was one of the biggest bait-n-switch and scam artist companies out there. In hopes of protecting all of my fellow POTN friends I made several posts warning folks, but my warnings and fears were proven wrong (at the time) as people were reporting back that they were getting exactly what was advertised. Now, fast-forward 3 months later, and folks are clearly being ripped off.
This really makes my heart sink because I don't want any of you to go through this, but unfortunately you are. If I were you, I would not even mess around with Big Value. Instead, I recommend that you immediately file a claim with eBay/PayPal, and then your credit card company if necessary. Folks, these people have a history of doing things like this and it dates back at least 8 years. And it's not going to stop. Besides rectifying your own situation, going after them through eBay may possibly help protect others from their deceit and bad business practices.
And don't even worry about the fact that you'll have to return it and won't have a Canon 5D in hand. I guarantee you that the rest of here on POTN will be watching closely and will find you a nearly equal deal on a shiny new Canon 5D Mark III sometime soon.
Best of luck to all of you affected by this! If I can think of ways to help, I certainly well.