title: Convert UTF-16 numbers to UTF-8?
body: <p>I have a iPad app where the user enters a phone number in a text field.  Sometimes the phone number is entered in UTF-16 (Japanese <em>sometimes</em> enter their phone numbers this way), but most of the time in UTF-8.</p>
  
  <p>My question is three-part:</p>
  
  <ul>
  <li>is there a way I can tell if the number is UTF-8 or UTF-16?</li>
  <li>how do I convert from UTF-16 to UTF-8, given the number is numeric?</li>
  <li>having looked and found nothing, anyone know of a good treatise on this subject? (converting back and forth in iOS).</li>
  </ul>