Your website wasn't deleted. Just disabled. The message you got was a discussion. Your site crashed the server. They have no choice but to disable it.
You need to see if all of that traffic is normal for you, just as their message said.
If so, then you do need a business account.
If not, then find a way to stop all of the unwanted traffic.
Once you decide what to do, you'll need to reply to them and let them know.