Dialing a command prefix on the iPhone

Question

Our application lets users call phone numbers. Users would like to be able to block their caller ID.

On other platforms, we let the user specify a custom dialing prefix. For instance, on my cell provider it's #31#.

I've tried two approaches so far.

First:

id url = [NSURL URLWithString: @"tel:#31#0000000"]
// produces nil

Second:

id encoder = ["#31#0000000" stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];
// produces %2331%230000000
id url = [NSURL URLWithString: [NSString stringWithFormat: @"tel:%@", encoded]];
// produces a valid-looking NSURL which doesn't do anything

I'm thinking at this point that I'm just not allowed to dial # and *, even from a Cocoa touch application. (I know it's not allowed from a web app.) Is this true, or am I missing something obvious?

Answer 1

It looks like there's intentionally no way to do this.