It would have asked for conformation and then for the password for your Apple ID account (or mobile confirmation through iPhone), before activating any subscription. All that just to prevent accidental subscribing.
There is a setting to not ask for the password for purchases, but it is off by default, and requires the password to activate that. All very intentional from a user’s perspective.
Apple TV+ starts with a 7 day free trial for regular new subscribers. Apple TV+ may offer a 3 months free trial to qualifying customers. There is no such thing as a 1 month subscription purchase, although it may say subscriptions with monthly fees (after any optional trial if applicable) have a “1 month” periodicity. If you have tried Apple TV+ before, then it would start with this month’s fee in advance for the upcoming ~30 days. Most subscriptions auto-renew until canceled. If you cancel during a trial (at least 24 hours before renewal), then no fees will be charged.
See your subscriptions overview - Apple
If you want to cancel a subscription from Apple - Apple Support
Request a refund for apps or content that you bought from Apple - Apple Support
