Saber Update name in PNR : Error = .ENTRY VALID ONLY FOR SUBSCRIBER PNR

Question

UpdateReservationRQ APi was working fine to update passsenger name in PNR. suddenly its returning error

<stl15:Warnings>
            <stl15:Warning>
               <stl15:Message>PARTIAL ERROR</stl15:Message>
            </stl15:Warning>
         </stl15:Warnings>
         <stl15:Errors>
            <stl15:Error UpdateId="ID-1">
               <stl15:Code>500900</stl15:Code>
               <stl15:Message>.ENTRY VALID ONLY FOR SUBSCRIBER PNR</stl15:Message>
            </stl15:Error>
         </stl15:Errors> 

I folowed steps to update name in PNR
1. Create session - SessionCreateRQ
2. Book ticket - EnhancedAirBookRQ
3. Create PNR - PassengerDetailsRQ
4. Read Itenary - TravelItineraryReadRQ
4. Update PNR - UpdateReservationRQ
below is the request for UpdateReservationRQ API

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:eb="http://www.ebxml.org/namespaces/messageHeader" xmlns:ns1="http://webservices.sabre.com/pnrbuilder/getres" xmlns:ns12="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns13="http://www.w3.org/1999/xlink" xmlns:ns14="http://www.w3.org/2000/09/xmldsig#" xmlns:or="http://services.sabre.com/res/or/v1_8" xmlns:ota="http://webservices.sabre.com/sabreXML/2003/07" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:stl1="http://webservices.sabre.com/pnrbuilder/v1_15" xmlns:stl2="http://services.sabre.com/STL/v01" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:wsse="http://schemas.xmlsoap.org/ws/2002/12/secext" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xml="http://www.w3.org/XML/1998/namespace">
    <SOAP-ENV:Header>
        <sec:Security xmlns:sec="http://schemas.xmlsoap.org/ws/2002/12/secext">
         <sec:BinarySecurityToken valueType="String" EncodingType="sec:Base64Binary">${#Project#sectoken}</sec:BinarySecurityToken>
       </sec:Security>
        <MessageHeader xmlns="http://www.ebxml.org/namespaces/messageHeader" version="1.0">
            <eb:From>
                <eb:PartyId type="urn:x12.org:IO5:01">99935345999</eb:PartyId>
            </eb:From>
            <eb:To>
                <eb:PartyId type="urn:x12.org:IO5:01">344535</eb:PartyId>
            </eb:To>
            <eb:CPAId>AB</eb:CPAId>
            <eb:ConversationId>cpm23432</eb:ConversationId>
            <eb:Service type="OTA">UpdateReservationOperation</eb:Service>
            <eb:Action>UpdateReservationRQ</eb:Action>
            <eb:MessageData>
                <eb:MessageId>608926</eb:MessageId>
                <eb:Timestamp>2017-05-22T15:49:07Z</eb:Timestamp>
            </eb:MessageData>
        </MessageHeader>
    </SOAP-ENV:Header>
    <SOAP-ENV:Body>
        <stl1:UpdateReservationRQ xmlns="http://webservices.sabre.com/pnrbuilder/v1_15" Version="1.15.0">
            <stl1:RequestType>Stateless</stl1:RequestType>
            <stl1:ReturnOptions IncludeUpdateDetails="true" RetrievePNR="true" />
            <stl1:ReservationUpdateList>
                <stl1:Locator>XPKCGL</stl1:Locator>
                <stl1:CreateDate>2017-05-23</stl1:CreateDate>
                <stl1:ReservationUpdateItem UpdateId="ID-1">
                    <stl1:PassengerNameUpdate op="U">
                        <stl1:TravelerName type="ADT" referenceId="1">
                            <stl1:Given>RamRaj</stl1:Given>
                            <stl1:Surname>Des</stl1:Surname>
                        </stl1:TravelerName>
                        <stl1:NameAssociationTag>
                            <stl1:LastName>DESHMUKH</stl1:LastName>
                            <stl1:FirstName>PRAVEEN</stl1:FirstName>
                            <stl1:NameRefNumber>01.01</stl1:NameRefNumber>
                        </stl1:NameAssociationTag>
                    </stl1:PassengerNameUpdate>
                </stl1:ReservationUpdateItem>
                <stl1:ReceivedFrom>
                    <stl1:AgentName>CPM MBE</stl1:AgentName>
                </stl1:ReceivedFrom>
            </stl1:ReservationUpdateList>
        </stl1:UpdateReservationRQ>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Any suggestion is appreciated to identify the issue in request or flow.

Answer 1

From Format Finder (ref pnrfo044):

• If the electronic ticket has not been issued, please refer to the name change restriction table for the carrier.
• Once an electronic ticket has been issued in a record, some carriers may allow a name change but others do not. Please refer to the electronic ticket profile for the specific validating carrier for name change restrictions.

You may need to check with the carrier if this is allowed or not.