There are so many questions this leaves unanswered:
- Was this a one-off error in Cloudflare's processes? (These things happen on a big enough scale.)
- Were you violating a specific clause of Cloudflare's T&C? How clear was the clause? What did you do to fix this?
- Was the issue that Cloudflare estimated that you're not paying enough given the bandwidth you're consuming? Did you end up signing up for the Enterprise plan?
Transparency would benefit both Cloudflare (in not making people unnecessarily apprehensive about becoming/remaining a customer) and you (in demonstrating that you're handling this issue in a professional and responsible manner).