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?

I would suggest making a contact in your address book with the specified phone number, then getting the information about that phone number programatically and see if you can find what it looks like. — Ed Marty, Apr 28 '10 at 01:52
Duplicate of http://stackoverflow.com/questions/4660951/problem-using-tel-with-star-asterisk — David d C e Freitas, Feb 24 '12 at 09:12
If by "duplicate" you mean "posted a year before." :P This was posted in April 2010, the question you say it's a duplicate of was posted in January 2011. — Steven Fisher, Feb 24 '12 at 17:55

Steven Fisher · Accepted Answer · 2013-09-19T18:14:00.940

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

To prevent users from maliciously redirecting phone calls or changing the behavior of a phone or account, the Phone application supports most, but not all, of the special characters in the tel scheme. Specifically, if a URL contains the * or # characters, the Phone application does not attempt to dial the corresponding phone number.

— Apple URL Scheme Reference Phone Links

Dialing a command prefix on the iPhone

1 Answers1