SalesOrderItem itemToUpdate = new SalesOrderItem();

		itemToUpdate.setLine(item.getLineNumber());
		itemToUpdate.setLineUniqueKey(item.getLineItemUniqueKey());
	   
		List<CustomFieldRef> customFieldRefs = new ArrayList<>();            
		SelectCustomFieldRef customFieldRef = new SelectCustomFieldRef();
		
		customFieldRef.setScriptId("custbody_target_audience");
		customFieldRef.setInternalId(String.valueOf(496));
		
		ListOrRecordRef listOrRecordRef = new ListOrRecordRef();
		listOrRecordRef.setInternalId(String.valueOf(1));
		listOrRecordRef.setTypeId(String.valueOf(95));
		listOrRecordRef.setName("Consumer");
		customFieldRef.setValue(listOrRecordRef);
		
		customFieldRefs.add(customFieldRef);
		
		CustomFieldList customFieldList = new CustomFieldList();
		customFieldList.setCustomField(customFieldRefs.toArray(new CustomFieldRef[customFieldRefs.size()]));
		
		itemToUpdate.setCustomFieldList(customFieldList);

		salesOrderItemsForUpdate.add(itemToUpdate);
			
			
		SalesOrder salesOrderToUpdate = new SalesOrder();
        salesOrderToUpdate.setInternalId(insertionOrderInternalID);
        
        SalesOrderItemList salesOrderItemList = new SalesOrderItemList();
        salesOrderItemList.setReplaceAll(false);
        salesOrderItemList.setItem(salesOrderItemsForUpdate.toArray(new SalesOrderItem[salesOrderItemsForUpdate.size()]));
        salesOrderToUpdate.setItemList(salesOrderItemList);
				
		this.getPort().update(salesOrderToUpdate);

===============================================================

Results in the following error - 


Error calling callUpdateRecord:  AxisFault   faultCode: {http://schemas.xmlsoap.org/soap/envelope/}Server.userException   faultSubcode:    faultString: org.xml.sax.SAXException: {urn:core_2018_1.platform.webservices.netsuite.com}CustomFieldRef is an abstract type and cannot be instantiated   faultActor:    faultNode:    faultDetail:   
  {http://xml.apache.org/axis/}hostname:partners002    org.xml.sax.SAXException: {urn:core_2018_1.platform.webservices.netsuite.com}CustomFieldRef is an abstract type and cannot be instantiated  
  at org.apache.axis.message.SOAPFaultBuilder.createFault(SOAPFaultBuilder.java:222)  
  at org.apache.axis.message.SOAPFaultBuilder.endElement(SOAPFaultBuilder.java:129)  
  at org.apache.axis.encoding.DeserializationContext.endElement(DeserializationContext.java:1087)  
  at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)  
  at org.apache.xerces.impl.XMLNSDocumentScannerImpl.scanEndElement(Unknown Source)  
  at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)  
  at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)  
  at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)  
  at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)  
  at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)  
  at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)  
  at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)  
  at org.apache.xerces.jaxp.SAXParserImpl.parse(Unknown Source)  
  at org.apache.axis.encoding.DeserializationContext.parse(DeserializationContext.java:227)  
  at org.apache.axis.SOAPPart.getAsSOAPEnvelope(SOAPPart.java:696)  
  at org.apache.axis.Message.getSOAPEnvelope(Message.java:435)  
  at org.apache.axis.handlers.soap.MustUnderstandChecker.invoke(MustUnderstandChecker.java:62)  
  at org.apache.axis.client.AxisClient.invoke(AxisClient.java:206)  
  at org.apache.axis.client.Call.invokeEngine(Call.java:2784)  
  at org.apache.axis.client.Call.invoke(Call.java:2767)  
  at org.apache.axis.client.Call.invoke(Call.java:2443)  
  at org.apache.axis.client.Call.invoke(Call.java:2366)  
  at org.apache.axis.client.Call.invoke(Call.java:1812)  
  at com.netsuite.webservices.platform_2018_1.NetSuiteBindingStub.update(NetSuiteBindingStub.java:15029)