Domains autorenew… even when deleted?

Months ago, two domains of mine were registered with Cloudflare; later they got transferred to another registrar and ISP, therefore I soon deleted them from Cloudflare.

Now they got auto-renewed… why on earth I got billed if they’re no longer on CF? I can’t access domains options, because they’re no longer here… besides asking a refund, I would like to know if I messed something on the way, and how to prevent similar issues in the future.

Thanks in advance for your help.
Gabriele