今天早上有个非常紧急的电话会议。。。。英文

There was a very urgent meeting call this morning. When we dialed the number you provided for the meeting, the call didn't response.

As you know, the meeting time couldn't be changed, so we had to hold the meeting through other way.

I think that it will be extremely inconvenient for us if the same problem happens again and again. So that I hereby want you to give us the cause regarding this issue.

Thank you!

按照楼主的意思，语气基本保持礼貌但又不失表达你们对此事的不满

最后那个让他们给一个答复，没有用reply，而是用cause ，表示你们想知道导致这个问题发生的原因。

As you know, there was a top urgent conference call this morning as per schedule, however when we dialed the telephone number your company provided for the conference call, it never worked! as the timing of the conference is fixed and couldn't be changed, we had to find other ways for the conference. I think if this similar thing occurs more than once, it will cause great inconvenience to our cooperation, so please give us