iOS App with Free trial and subscribe after that
The App Store Review Guidelines are clear, an app that expires will be rejected:


  11.9 Apps containing content or services that expire after a limited time will be rejected, except for specific approved content (e.g. films, television programs, music, books)


Contact Apple

Talk to Apple's App Store staff about how best to approach your app and how to avoid being rejected:


  App Review
  
  Find out the status of your app and submit general questions for the App Review Team.