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
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
End a pull notification subscription.
 @see http://msdn.microsoft.com/en-us/library/aa564263.aspx

 @param [String] subscription_id The Id of the subscription