PhoneAuthentication is null while getting the Recipients from Docusign package using Docusign .net PKG while it is present in package at account.

PhoneAuthentication is received as null.

Code used to add Authentication is below: 

orignalSigners.IdCheckConfigurationName = "Phone Auth $";
                                    RecipientPhoneAuthentication recipientPhoneAuthentication = new RecipientPhoneAuthentication();
                                    List<string> senderProvidedNumbers = new List<string>();
                                    recipientPhoneAuthentication.SenderProvidedNumbers = senderProvidedNumbers;
                                    recipientPhoneAuthentication.SenderProvidedNumbers.Add(t.PhoneNumber);
                                    orignalSigners.PhoneAuthentication = recipientPhoneAuthentication;

Trying to get Signer with Authentication using following code but the signer.PhoneAuthentication is received as null:

System.Net.ServicePointManager.SecurityProtocol = (System.Net.SecurityProtocolType)3072;
                accountID = this.GetAccountID();
                EnvelopesApi envelopesApi = new EnvelopesApi(apiClient);
                envelopesApi.ApiClient = apiClient;
                Recipients results = envelopesApi.ListRecipients(accountID, envelopID);
                Envelope envelop = envelopesApi.GetEnvelope(accountID, envelopID);

                signerList = results.Signers;
                dict = new Dictionary<Envelope, List<Signer>>();
                dict.Add(envelop, signerList);

Please help me figure out what I am doing wrong while reading the recipients