If you purchased a custom domain from Namecheap within the Adobe Portfolio Editor, your custom domain is automatically set to renew.
Before your custom domain name is set to renew, Namecheap will send an email with a link to disable the upcoming auto-renewal. In order to disable auto-renewal, you will need to click that link in tht email to turn auto-renewal off.
Note: turning auto-renew off within your Namecheap account will not disable auto-renew. You need to cancel auto-renew using the email link.