iPhone app "rejecting" incoming calls?

Question

A client of mine just informed me that, while using the app I am developing for them, they received an incoming call, but it did not bring up an alert on the iPhone. Instead, the person making the call heard a message that the user's service was temporarily unavailable.

If we put aside for a moment the possibility that either the person making the call did not have a signal to make a call, or that my client did not have a signal to receive a call, is there any conceivable way that my app could have silently rejected the call? I don't think that's possible. My interpretation of the Apple docs tells me the iPhone OS is in full control and should be able to terminate my app if it wanted.

Am I missing any corner cases here?

Answer 1

Assuming your client is in the US, remind him how much AT&T sucks. There's absolutely no way that you can block a phone call from coming in.

Answer 2

You're right. There's no way for an application to stop a call from coming in.

The only thing your application can do is be notified that you're getting shutdown because a call is coming in, as the link you provided describes.

Answer 3

Are they on EDGE? While using EDGE, you can't receive calls. They share the same radio.

Answer 4

Had a similar problem a while ago, but it "disappeared" before I could really dig into it.

What seemed to be happening:

• My App was doing some heavy calculations in a very tight loop.
• The upper half of the "call incoming" interrupt was handled.
• The bottom half was called "to late".
• The call was dropped.

This has in no way been confirmed by apple or any other developer. The phone I was working on was ... slightly modified, so it might have been totally our fault.

The loop has since been removed and the problem never showed up again.