diff --git a/i18n/en-US.json b/i18n/en-US.json
index 2cc4871d..8d10b3d2 100644
--- a/i18n/en-US.json
+++ b/i18n/en-US.json
@@ -481,6 +481,7 @@
 		"add": "Add User",
 		"addExtension": "Add an extension to this user",
 		"addNewExtension": "Extension number: ",
+		"extensionAlreadyExist": "Already exists",
 		"addFromSpare": "Add from Spare Numbers",
 		"addFromSpareDevices": "Add from Spare Devices",
 		"buy": "Buy Numbers",
diff --git a/submodules/users/users.js b/submodules/users/users.js
index b3f6e375..8b26c2ec 100644
--- a/submodules/users/users.js
+++ b/submodules/users/users.js
@@ -833,6 +833,21 @@ define(function(require) {
 				listExtensions.append(newLineTemplate);
 
 				existingExtensions.push(nextExtension);
+
+				newLineTemplate.find('.extesion-already-exist').hide();
+
+				newLineTemplate.find('.input-extension ').on('keyup', function() {
+					var val = $(this).val();
+
+					if (existingExtensions.indexOf(val) >= 0) {
+						newLineTemplate.find('.extesion-already-exist').show();
+						template.find('.save-extensions').attr('disabled', true)
+						return;
+					}
+
+					newLineTemplate.find('.extesion-already-exist').hide();
+					template.find('.save-extensions').attr('disabled', false)
+				});
 			});
 
 			template.on('click', '.remove-extension', function() {
@@ -854,6 +869,7 @@ define(function(require) {
 
 				if (index > -1) {
 					existingExtensions.splice(index, 1);
+					template.find('.save-extensions').attr('disabled', false)
 				}
 
 				$(this).parents('.item-row').remove();
@@ -4896,7 +4912,7 @@ define(function(require) {
 					}, function(devices) {
 						callback(null, devices);
 					});
-				}
+				},
 			}, function(err, results) {
 				callback && callback(results);
 			});
diff --git a/submodules/users/users.scss b/submodules/users/users.scss
index 59412f65..9ae2cd5b 100644
--- a/submodules/users/users.scss
+++ b/submodules/users/users.scss
@@ -456,6 +456,15 @@
 	line-height: 32px;
 }
 
+#users_container .list-wrapper .item-row .extesion-already-exist {
+	margin: 0;
+	padding: 0;
+	font-size: 12px;
+	font-style: italic;
+	color: #ee1212;
+	font-weight: 600;
+}
+
 #users_container .list-wrapper .empty-search-row,
 #users_container .list-wrapper .empty-row {
 	display: none;
diff --git a/submodules/users/views/newExtension.html b/submodules/users/views/newExtension.html
index 43bd9427..9380a23a 100644
--- a/submodules/users/views/newExtension.html
+++ b/submodules/users/views/newExtension.html
@@ -1,7 +1,8 @@
 <div class="item-row larger">
     <div class="number">
-		{{ i18n.users.addNewExtension }}
-		<input type="text" class="input-extension" value="{{recommendedExtension}}"></input>
-		<a class="cancel-extension-link monster-link"><i class="monster-red fa fa-times"></i></a>
+			{{ i18n.users.addNewExtension }}
+			<input type="text" class="input-extension" value="{{recommendedExtension}}"></input>
+			<a class="cancel-extension-link monster-link"><i class="monster-red fa fa-times"></i></a>
     </div>
+		<p class="extesion-already-exist">{{ i18n.users.extensionAlreadyExist }}</p>
 </div>