But this time, specify the PhoneNumber parameter like this: <a href="http://companyfoo.com/hello-client-twiml.cshtml?PhoneNumber=14158675309Since">http://companyfoo.com/hello-client-twiml.cshtml?PhoneNumber=14158675309Since</a> we want to be able to call phone numbers or other clients, we have made the TwiML script accept either.