diff --git a/sdk/communication/communication-calling-server/review/communication-calling-server.api.md b/sdk/communication/communication-calling-server/review/communication-calling-server.api.md
index 96c36f8dd990..2b8fbf68cfe8 100644
--- a/sdk/communication/communication-calling-server/review/communication-calling-server.api.md
+++ b/sdk/communication/communication-calling-server/review/communication-calling-server.api.md
@@ -16,7 +16,7 @@ import { TransferProgressEvent } from '@azure/core-http';
 
 // @public
 export interface AddParticipantOptions extends OperationOptions {
-    alternateCallerId?: string;
+    alternateCallerId?: PhoneNumberIdentifier;
     operationContext?: string;
 }
 
@@ -395,7 +395,7 @@ export interface TransferToCallOptions extends OperationOptions {
 
 // @public
 export interface TransferToParticipantOptions extends OperationOptions {
-    alternateCallerId?: string;
+    alternateCallerId?: PhoneNumberIdentifier;
     operationContext?: string;
     userToUserInformation?: string;
 }
diff --git a/sdk/communication/communication-calling-server/src/callConnection.ts b/sdk/communication/communication-calling-server/src/callConnection.ts
index 82d1367c5061..c86643ac4d78 100644
--- a/sdk/communication/communication-calling-server/src/callConnection.ts
+++ b/sdk/communication/communication-calling-server/src/callConnection.ts
@@ -462,10 +462,11 @@ export class CallConnectionImpl implements CallConnection {
       operationOptions
     );
     const alternateCallerId =
-      typeof restOptions?.alternateCallerId === "undefined"
-        ? restOptions?.alternateCallerId
-        : serializeCommunicationIdentifier({ phoneNumber: restOptions.alternateCallerId })
-            .phoneNumber;
+      restOptions.alternateCallerId == null
+        ? undefined
+        : serializeCommunicationIdentifier({
+            phoneNumber: restOptions.alternateCallerId.phoneNumber
+          }).phoneNumber;
 
     const request: AddParticipantRequest = {
       participant: serializeCommunicationIdentifier(participant),
@@ -762,10 +763,11 @@ export class CallConnectionImpl implements CallConnection {
     );
 
     const alternateCallerId =
-      typeof restOptions?.alternateCallerId === "undefined"
-        ? restOptions?.alternateCallerId
-        : serializeCommunicationIdentifier({ phoneNumber: restOptions.alternateCallerId })
-            .phoneNumber;
+      restOptions.alternateCallerId == null
+        ? undefined
+        : serializeCommunicationIdentifier({
+            phoneNumber: restOptions.alternateCallerId.phoneNumber
+          }).phoneNumber;
 
     const request: TransferToParticipantRequest = {
       targetParticipant: serializeCommunicationIdentifier(targetParticipant),
diff --git a/sdk/communication/communication-calling-server/src/callingServerClient.ts b/sdk/communication/communication-calling-server/src/callingServerClient.ts
index 92f14d7e58af..accc87001649 100644
--- a/sdk/communication/communication-calling-server/src/callingServerClient.ts
+++ b/sdk/communication/communication-calling-server/src/callingServerClient.ts
@@ -192,17 +192,20 @@ export class CallingServerClient {
       operationOptions
     );
 
+    const alternateCallerId =
+      restOptions.alternateCallerId == null
+        ? undefined
+        : serializeCommunicationIdentifier({
+            phoneNumber: restOptions.alternateCallerId.phoneNumber
+          }).phoneNumber;
+
     const request: CreateCallRequest = {
       source: serializeCommunicationIdentifier(source),
       targets: targets.map((m) => serializeCommunicationIdentifier(m)),
       callbackUri: restOptions.callbackUrl,
       requestedMediaTypes: restOptions.requestedMediaTypes,
       requestedCallEvents: restOptions.requestedCallEvents,
-      alternateCallerId:
-        restOptions.alternateCallerId == null
-          ? undefined
-          : { value: restOptions.alternateCallerId.phoneNumber },
-      subject: restOptions.subject
+      alternateCallerId: alternateCallerId
     };
 
     try {
@@ -379,16 +382,17 @@ export class CallingServerClient {
       "ServerCallRestClient-AddParticipant",
       operationOptions
     );
-    const alternate_caller_id =
-      typeof restOptions?.alternateCallerId === "undefined"
-        ? restOptions?.alternateCallerId
-        : serializeCommunicationIdentifier({ phoneNumber: restOptions.alternateCallerId })
-            .phoneNumber;
+    const alternateCallerId =
+      restOptions.alternateCallerId == null
+        ? undefined
+        : serializeCommunicationIdentifier({
+            phoneNumber: restOptions.alternateCallerId.phoneNumber
+          }).phoneNumber;
 
     const request: AddParticipantWithCallLocatorRequest = {
       callLocator: callLocator,
       participant: serializeCommunicationIdentifier(participant),
-      alternateCallerId: alternate_caller_id,
+      alternateCallerId: alternateCallerId,
       operationContext: restOptions?.operationContext,
       callbackUri: callbackUrl
     };
diff --git a/sdk/communication/communication-calling-server/src/models.ts b/sdk/communication/communication-calling-server/src/models.ts
index 8cbaec2662b5..1a424bdacf0c 100644
--- a/sdk/communication/communication-calling-server/src/models.ts
+++ b/sdk/communication/communication-calling-server/src/models.ts
@@ -86,7 +86,7 @@ export interface PlayAudioOptions extends OperationOptions {
  */
 export interface TransferToParticipantOptions extends OperationOptions {
   /** The alternate identity of the source of the call if dialing out to a pstn number */
-  alternateCallerId?: string;
+  alternateCallerId?: PhoneNumberIdentifier;
   /** The user to user information. */
   userToUserInformation?: string;
   /** The value to identify context of the operation. */
@@ -112,8 +112,8 @@ export type PlayAudioToParticipantOptions = PlayAudioOptions;
  * Options to add participant to the call.
  */
 export interface AddParticipantOptions extends OperationOptions {
-  /** The phone number to use when adding a pstn participant. */
-  alternateCallerId?: string;
+  /** The phone number identity to use when adding a pstn participant. */
+  alternateCallerId?: PhoneNumberIdentifier;
   /** The operation context. */
   operationContext?: string;
 }