They were upset that I was unreachable by phone and not returning messages.

他们会因我不接电话，不回他们信息而生气。

Send email to colleague who returns a WhatsApp message with the answer.

给一位同事发邮件，他会在WhatsApp上回复。

I called the doctor;the doctor did not return my message.

我打电话给医生，医生没有回我的消息。

He never took her calls or returned her messages.

不再接她电话，也不回她留言。

I guess if you're taking over, then you should probably return these messages.

既然你要自己处理 那就要回覆这些留言。

You would talk into a funnel-shaped contrivance and then place it against your ear to get the returning message.

你会对着一个漏斗形的装置说话， 然后把它放在你的耳朵上以获得返回的信息。