Unsubscribe the app when its past the extension deadline and doesn’t have button for cancel

You can unsubscribe from an app at any time. There is no extension deadline. It's only if you are too late to avoid the next renewal period that it automatically renews. However, if it does that you can still cancel the subscription, it will just run until the end of that period and not renew. Your not seeing the Cancel button suggests that you may have already canceled it, it's just running until the end of the current subscription.

This support article explains how to cancel a subscription from Apple on various kinds of hardware and online ➔ Cancel a subscription from Apple - Apple Support Use the drag-down menu to choose the kind of equipment you have.

Notes:

• “If you signed up for a trial subscription and you don't want to renew it, cancel it at least 24 hours before the trial ends.” Exceptions in: About canceling subscriptions in Germany, Israel, South Africa, or Türkiye - Apple Support

• Free trials will usually automatically turn into paid subscriptions unless you cancel in time.

• Many subscriptions are set to renew automatically until you intentionally cancel them.

• If you don’t see Cancel Subscription, then the subscription is already canceled and won't renew. An "Expires" date (instead of "Renews") means the current subscription has been canceled but will work until the expiration date. "Resubscribe" (or Renew) is just in case you change your mind about having it end.

• Deleting an app does not cancel a subscription.

If you go to Settings > [your name] > Subscriptions > [this subscription] on your iPhone, don’t you see a “Cancel Subscription” on the bottom? That would end your subscription once your current subscription expires.