I know how to call phone number (e.g. 12345678) from iPhone App using:
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"tel:12345678"]];
But for phone numbers with * or #, the above line is not responding (no error message as well):
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"tel:*777"]];
The answer is : iOS SDK does not allow phone numbers with * or # to be dialed in app.
Reference: Call to a number, which contain #. (IPhone SDK)