How can I change my subscription period?

You can manage your subscription plan in your Apple ID settings; however, according to the App Store procedures, it can only be changed to a new one when your current subscription is up. Therefore, to upgrade your subscription, you first need to cancel your current subscription and then purchase a new one.

After you cancel, your current subscription will stop at the end of the current billing cycle. Then (or sometime before the expiration, if you want to retain continuous access to the app), you can switch to another subscription.

Please also make sure you cancel your current plan at least 24 hours before the next billing period to avoid being charged for the renewal.

For more details, please contact Apple Support directly, as they manage all transactions and subscription plans.