MaxProtocolVersion error - SAP Gateway for Microsoft

Hi,

I'm receiving the following error after executing the following code. serviceContext returns MaxProtocolVersion as read only. How to modify MaxProtocolVersion and resolve this issue.

ServiceDetails serviceDetail = ConfigurationReaderHandler.Instance.GetServiceDetails("ZPURCHASE_ORDER_SRV");
serviceContext = new ZPURCHASE_ORDER_SRV(new Uri(serviceDetail.Url));
serviceContext.AddAndUpdateResponsePreference = DataServiceResponsePreference.IncludeContent;//error
//data fill - poItem
serviceContext.AddObject("ZPURCHASE_ORDER_SRV", poItem);
DataServiceResponse response = serviceContext.SaveChanges();