In your own documentation you show how a user can cancel their Zoho CRM subscription.
-> https://help.zoho.com/portal/en/kb/crm-plus/admin-guide/subscription-information/articles/cancel-subscriptions




But for my customer, there is no "Cancel Subscription" button.

Now if this is intentional, its very anti-consumer behaviour making it a difficult experience for a user to be able to cancel a subscription.