I read Upgrades, Downgrades, & Management where it says:
There are no code changes required to support upgrades, downgrades, and crossgrades for iOS subscriptions in your app. A customer can choose to upgrade, downgrade, or crossgrade between subscriptions as often as they like.
I know this is possible externally from the the iPhone Settings “Manage Subscriptions” page.
I want to know if it’s possible internally from the app.
For example, the app presents an annual subscription paywall to a monthly subscriber. If the user tries to subscribe to the annual plan, will it seamlessly switch subscriptions?
In the past, attempting to purchase the same subscription within the same group returns an error. I’m cautiously shipping both approaches: internal paywall and redirect to external settings.