How do I cancel my 'Clean Now' subscription on iPhone?

For any subscription that was started with an in-app purchase, you can cancel that here:

View or cancel app subscriptions on iPhone - Apple Support

If you started a free trial or a subscription with the developer directly on their website, then that is not managed by Apple and you will not see it in the link above. For any subscription that does not involve Apple, you will have to use that same website where it was started to cancel it.

I don’t have a subscription to that, so I couldn’t cancel it.