1. Complaining about bans on the forums is a good way to receive one here.
2. Try the Support portal instead: http://wiki.spiralknights.com/Support_Portal
3. /1 (Zone Chat) is not for trading. /2 (Trade Chat) was added so that people would no longer trade in Zone chat.
4. Someone probably reported you and OOO took a bit to respond to it. When reported, it sends a chat log with it so they didn't need to be there for it.
5. Paying money does not exempt you from the rules.
Spamming is clearly defined in the Terms of Service:
http://www.spiralknights.com/tos.xhtml
Spamming
Don't spam! - Use the chat client sensibly, just like you would when talking to someone in person. Spamming is defined as repeatedly sending letters, messages or nonsense in a way that makes it difficult for other knights to communicate. Spamming is not acceptable in any form.
It sounds to me like you were spamming, which is against the Terms, and received the just punishment.
Wow this is a troll thread. Read the TOS about appealing your ban, and about not complaining about it on the fourms.