我在张满胜老师的书中看到这样一个虚拟语气的句子I'm sorry you felt that a call with our producer to personally apologize would have been insufficient. However, to repeat, we're writing again to offer our sincere apology.

这句话的背景是这句话的背景是：2013年10⽉22⽇美国当地华⽂媒体报道指出，美国⼴播公司（ABC）深夜脱⼝秀节⽬中，⼀名⼉童在回答主持⼈吉⽶·凯梅尔（Jimmy Kimmel）的提问“美国如何偿还⽋中国的1.3万亿美元”时脱⼝⽽出，“要绕到地球另⼀边去，杀光中国⼈”。节⽬⼀经播出，⽴即引起当地华⼈⺠众的抗议。这句话摘自美国广播公司道歉信。张老师认为，这个电话并没有打，他说到：“如果电话打过了，⽽且中⽅依然认为电话道歉不够就会把过去虚拟形式would have been改为⼀般过去时态was，即...a call with our producer to personally apologize was insufficient.”

我觉得would have been如果是虚拟语气，可能会有一个隐藏条件，我问了问WR的友友们，其中一个人告诉我说确实有，可以理解为if the call had been made,另一位友友提供了一个思路The phrase "I'm sorry you felt that ..." in yor OP suggests that the addressee, some time in the past, said: "...a call with your producer [...] will be insufficient." And that would suggest that 'would have been' is reported speech of 'will be' (assuming that the direct speech statement happened well before reported speech, 'would have been' instead of 'would be' makes sense without knowing other details that happened since then).But that fact is academic; it's only useful for syntactical analysis. It does not truly change the idea the OP sentence wants to express.我觉得这位友友提供给我的信息让我更疑惑了，我觉得直接引语和间接引语讲得是的一个事情怎么还有发生的先后顺序我就不太理解了，更别说 without knowing other details that happened since then 了，不知道是不是我理解错了。

所以我对这个句子理解不好，有点混乱，想请问各位老师，到底应该怎么理解这个would have been。