title: Intercepting incoming calls on iPhone
body: <p>I would like to write software for my iPhone that intercepts incoming calls, and requires that the caller press "1" to proceed with the call. (This is for fighting telemarketers.)</p>
  
  <p>I would prefer to write the software myself, and not install an app like Hiya.</p>
  
  <p>I have a regular phone number assigned by my carrier (no fancy Google Voice or VOIP stuff), and I use the standard "Phone" app. My phone is not jail-broken.</p>
  
  <p><strong>What's the simplest way to intercept an incoming call to the standard "Phone" app?</strong></p>
  
  <p>(This is inspired by the <a href="http://www.jollyrogertelco.com/" rel="nofollow noreferrer">Jolly Roger Telephone Company</a> anti-telemarketer bot.)</p>
  
  <p>Note: Some old threads (<a href="https://stackoverflow.com/questions/12026233/ios-application-intercept-incoming-calls-and-redirect-them-to-voice-mail">here</a>, <a href="https://stackoverflow.com/questions/20119474/intercept-incoming-call-ios-sdk-non-jailbreak">here</a>) say it's impossible, but <a href="https://stackoverflow.com/questions/39669421/how-to-intercept-messages-sent-from-callkit-incoming-call-screen">this</a> thread mentions iOS 10's "CallKit" framework, but it seems it's geared more toward VOIP apps. So it seems like it might be possible.</p>
  
  <p>Thanks.</p>