diff --git a/src/Bandwidth.Standard.Test/Unit/Model/Bxml/TestPhoneNumber.cs b/src/Bandwidth.Standard.Test/Unit/Model/Bxml/TestPhoneNumber.cs
index 17a061c..0514f8b 100644
--- a/src/Bandwidth.Standard.Test/Unit/Model/Bxml/TestPhoneNumber.cs
+++ b/src/Bandwidth.Standard.Test/Unit/Model/Bxml/TestPhoneNumber.cs
@@ -10,7 +10,7 @@ public class TestPhoneNumber
 		[Fact]
 		public void PhoneNumberTest()
 		{
-			var expected = "<?xml version=\"1.0\" encoding=\"utf-8\"?><Response>  <PhoneNumber transferAnswerUrl=\"https://test.url/\" transferAnswerMethod=\"POST\" transferAnswerFallbackUrl=\"https://fallbackTest.url/\" transferAnswerFallbackMethod=\"POST\" transferDisconnectUrl=\"https://disconnectTest.url/\" transferDisconnectMethod=\"POST\" username=\"username\" password=\"password\" fallbackUsername=\"fallbackUsername\" fallbackPassword=\"fallbackPassword\" tag=\"test\">+15551234567</PhoneNumber></Response>";
+			var expected = "<?xml version=\"1.0\" encoding=\"utf-8\"?><Response>  <PhoneNumber transferAnswerUrl=\"https://test.url/\" transferAnswerMethod=\"POST\" transferAnswerFallbackUrl=\"https://fallbackTest.url/\" transferAnswerFallbackMethod=\"POST\" transferDisconnectUrl=\"https://disconnectTest.url/\" transferDisconnectMethod=\"POST\" username=\"username\" password=\"password\" fallbackUsername=\"fallbackUsername\" fallbackPassword=\"fallbackPassword\" tag=\"test\" uui=\"testUUI\">+15551234567</PhoneNumber></Response>";
 
 			var phoneNumber = new PhoneNumber();
 			phoneNumber.Number = "+15551234567";
@@ -25,6 +25,7 @@ public void PhoneNumberTest()
 			phoneNumber.FallbackUsername = "fallbackUsername";
 			phoneNumber.FallbackPassword = "fallbackPassword";
 			phoneNumber.Tag = "test";
+			phoneNumber.UUI = "testUUI";
 
 			var response = new Response(phoneNumber);
 			var actual = response.ToBXML();
diff --git a/src/Bandwidth.Standard/Model/Bxml/Verbs/PhoneNumber.cs b/src/Bandwidth.Standard/Model/Bxml/Verbs/PhoneNumber.cs
index 0125b46..cfeceac 100644
--- a/src/Bandwidth.Standard/Model/Bxml/Verbs/PhoneNumber.cs
+++ b/src/Bandwidth.Standard/Model/Bxml/Verbs/PhoneNumber.cs
@@ -77,10 +77,15 @@ public class PhoneNumber : IVerb
         public string FallbackPassword { get; set; }
 
         /// <summary>
-        /// Optional custom string to include in callbacks.
+        /// (optional) Custom string to include in callbacks.
         /// </summary>
         [XmlAttribute("tag")]
         public string Tag { get; set; }
 
+        /// <summary>
+        /// (optional) The value of the User-To-User header to send within the initial INVITE.
+        /// </summary>
+        [XmlAttribute("uui")]
+        public string UUI { get; set; }
     }
 }