title: Auth0 Passwordless Request - Error 21211 - Phone Number format
body: <p>I am using the Auth0.AuthenticationApi for Passwordless. I have set up my client with Twilio Trial account and populated the Live Credentials of SID and AuthToken. When I make a call to <code>StartPasswordlessSmsFlowAsync</code> I get an error message about the format of the 'To' Phone Number. I have tried URL Encoding the Phone number as suggested in another post.</p>
  
  <p>See code below.</p>
  
  <pre><code>    PasswordlessSmsRequest request = new PasswordlessSmsRequest();
      request.ClientId = "D2E7BMKdT6q6fBLi*****************";
      request.PhoneNumber = System.Net.WebUtility.UrlEncode(phoneNumber); // +353123456789
      var response = client.StartPasswordlessSmsFlowAsync(request);
  </code></pre>
  
  <p>This results in the error 21211:</p>
  
  <pre><code>    String does not match pattern: ^\+[0-9]{1,15}$
  </code></pre>
  
  <p>I have also tried to use the 'Try' feature under the Passwordless connections but that gives the same error.</p>
  
  <p>Can someone please help out?</p>