You say "I was banned and have no clue why" because it works. When I botted wow, I would get banned all the time and play stupid, sometimes I had used a proxy so I adamantly deny and suggest maybe I got hacked. It works more than you think, never admit guilt because well that will sink your ship. I think the most unbans I got for one wow account was 8 within 2 months. You dont know what they have evidence why, or what it was they banned you for. So don't spill your guts, just play stupid and let them show you what they found or if they really had nothing.
I guess its kind of like getting a speed ticket, "do you know how fast you were going sir?" you say no, or have no idea, or some excuse. If you end up wanting to fight the ticket and you said yeah I know how fast and admit to the cop, you're sunk.
It is sad that some dupers got unbanned/never banned while others were banned. This is the first game where I have been banned, then offered a refund though. But you never know until you try. I figured after appealing three times, it would be better to get refund and buy someone else's account.. why? because their customer support takes fucking forever, I still never got called like I requested, over month ago now that I tihnk of it. But also because I was unbanned and told I was innocent, then banned, then told "superior decided it and thats final no evidence" all within 2 days. With that said, day 16 or 18 on ban appeal? I would have gotten another account, so many cheap deals and you can change pretty much everything in account management.