You cannot dial a number containing * or # characters. Apple doesn't allow them in a dial string for security reasons.
Apple Documentation says :
To prevent users from maliciously redirecting phone calls or changing
the behavior of a phone or account, the Phone app supports most, but
not all, of the special characters in the tel scheme. Specifically, if
a URL contains the * or # characters, the Phone app does not attempt
to dial the corresponding phone number. If your app receives URL
strings from the user or an unknown source, you should also make sure
that any special characters that might not be appropriate in a URL are
escaped properly. For native apps, use the
stringByAddingPercentEscapesUsingEncoding: method of NSString to
escape characters, which returns a properly escaped version of your
original string.
