How do I check my iPhone's subscription details?

What exactly happened that makes you think you were re-subscribed?

To re-subscribe you need to confirm with your password or touch or Face ID, it does not happen with a single tap.

All subscriptions will show either "Renews On and a date" for active subscriptions or "Expires on and a date" for canceled ones, and "Expired on and a date" for expired ones.

Tapping on those, does not in any way automatically re-subscribe you.

Can you post a screen shot of these subscriptions?

Are you sure you canceled them originally?

So, how do you know that charge was for one of those subscriptions?

If the name of the app or service appears on your payment method's statement, then it was subscribed and charged directly by the provider. Apple and your Apple account associated subscriptions would have nothing to do with it. You would need to cancel them directly with the provider.

For subscriptions charged through Apple that appear on your Apple account, they would only show up as "apple.com/bill" on your statement. If it showed up as that, it's possible the charge was for something other than the cancelled subscriptions in that case.

I can touch the name of a subscription without it resubscribing me so I have no idea how it could have happened to you. I normally don't purchase anything until I have double-clicked the side-button of the device. Do you not get that?