Unable to add PSTN participant using Call Automation

I am using Call Automation client to add the participant to a call.
Document to refererence - https://learn.microsoft.com/en-gb/azure/communication-services/how-tos/call-automation/actions-for-call-control?tabs=javascript#add-a-participant-to-a-call

Here is the process-

From number - +13097392188(Azure number )
to number - +19473451543(Azure Number)

Using Azure "Try Phone Calling" we are initiating a call from above number

Once call is ringing we are answering the call by subscribing to "IncomingCall Event"

const incomingCallContext = "<IncomingCallContext_From_IncomingCall_Event>"; 
const callbackUri = "https://<myendpoint>/Events"; 
const { callConnection } = await client.answerCall(incomingCallContext, callbackUri);

Once answered we are adding a participant using communicationUserId:

const customCallingContext = []; 
customContext.push({ kind: "voip", key: "voipHeaderName", value: "voipHeaderValue" })

const addThisPerson = {
    targetParticipant: { communicationUserId: "<acs_user_id>" },
    customCallingContext: customCallingContext,
};
const addParticipantResult = await callConnection.addParticipant(addThisPerson, {
            operationCallbackUrl: "<url_endpoint>",
            operationContext: "<operation_context>"
});

And using below at client side, we recieve the call at client side.

import {
  CallClient,
  CallAgentKind,
  } from '@azure/communication-calling';
import { AzureCommunicationTokenCredential, createIdentifierFromRawId } from '@azure/communication-common';


const tokenCredential = new AzureCommunicationTokenCredential("<TOKEN>");
        const callClient = new CallClient();
        console.log({ identity, token:"<TOKEN>", tokenCredential });
        const agent = await callClient.createCallAgent(tokenCredential, {
          kind: CallAgentKind.CommunicationUser,
});

window.deviceManager = await callClient.getDeviceManager();
const permissions = await window.deviceManager.askDevicePermission({ audio: true, video: false });


agent.on('incomingCall', async (args) => {
const call = args.incomingCall;
const callInstance = await call.accept();
})

This works perfectly fine!!

But when I try to add the PSTN number,
Getting error - "SourceCallerIdNumber or TeamsAppSource should be specified when calling or adding a PSTN number"

I am providing the sourcecallerID - <To Number defined above>

const addThisPerson = {
      targetParticipant: transferDestination,
      sourceCallIdNumber: '+19473451543',
      customCallingContext: [],
    };

  await callConnection.addParticipant(addThisPerson);

Can you help me out what I am missing while adding PSTN number?