Question

请问这句的句子成分是？越详细越好，谢谢。

There is normally no refund should a client choose to cancel
客户若要取消服务，通常不予退款。

Answer 1

There is normally no refund 由 There is 引导的主语：通常不予退款
should a client choose to cancel = if a client should choose to cancel. 虚拟语气， 省去if, 将should 提前。