You went to their website and got a free reading that if you had seen the fine print also said that the free reading was included in your subscription. You were most likely directed to this site from a user on Social Media that was paid to get you to go there or from a website advertisement. When you sign up for any free trial, you give them your payment information, as it is standard practice for a free trial to be billed as a subscription if it is not cancelled during the trial period..
A subscription made with any third party service does not involve Apple at all. Apple can only manage a subscription when it is made with an in-app purchase. This is true for other services as well even if they also have an app. For example Netflix, YouTube, X, and SnapChat all have subscriptions that can be made directly with them to bypass Apple's ability to manage the subscription.
You will need to cancel the subscription on that same website where you were directed. If you are unable to get help from their support, then you will have to dispute the charge with the bank that issued your card and also make sure they block any further charges.
In addition, depending on the site/user that directed you there, I would warn other users there of the consequences of following any link that was suggested at that location. It has been seen frequently on Facebook and SnapChat. If there was a subscription made through an in-app purchase, it is easily cancelled here, but I am guessing that is not what was done in your case:
View or cancel app subscriptions on iPhone - Apple Support