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You can't use the extension number directly to make a ring-out call. However, you can use the main company number and the extension number as shown below:

var params = {
      'from' : { 'phoneNumber': "16501112222*102" }, // provided the 102 extension number exists and belongs to the account
      'to'   : {'phoneNumber': "16503334444"},
      'playPrompt' : false
    }