title: iOS IAP with auto renew subscription that has multiple products in the same family with the same duration
body: <p>I'm currently working on an iOS app that will allow users to purchase an auto-renew subscription to access service charged monthly.  I would like to be able to offer a basic and premium service, and allow users to upgrade or downgrade from one or the other.  </p>
  
  <p>I've set up test users and some test products and I've found that if you select the basic subscription first and then later on select to purchase the premium subscription the test user is charged for both services simultaneously.</p>
  
  <p>Does anyone know if its possible to programmatically cancel a users current subscription when we've noticed they've either upgraded or downgraded their service, so they are only being charged once?</p>
  
  <p>I've seen that using this link
  <a href="https://buy.itunes.apple.com/WebObjects/MZFinance.woa/wa/manageSubscriptions" rel="nofollow">https://buy.itunes.apple.com/WebObjects/MZFinance.woa/wa/manageSubscriptions</a>
  Allows a user to manage their subscriptions manually, but I would like to handle migrating them to their new plan automatically.  </p>