code: def unsubscribe(subscription_id)
        req = build_soap! do |type, builder|
          if(type == :header)
          else
            builder.nbuild.Unsubscribe {
              builder.nbuild.parent.default_namespace = @default_ns
              builder.subscription_id!(subscription_id)
            }
          end
        end
        do_soap_request(req, response_class: EwsResponse)
      end
docs: End a pull notification subscription.
   @see http://msdn.microsoft.com/en-us/library/aa564263.aspx
  
   @param [String] subscription_id The Id of the subscription