Anyone who initiates a call should speak first and not the receiver.

The conversation usually starts with the greeting "hello." and followed by an introduction."This is XYZ from ABC Limited...am I speaking with 123"

In this way, the receiver need not ask, "Who is this, please?"

In the case you highlighted, the same principle applies. The caller should speak first by saying "hello" even when the receiver have their number saved. This opens the line for conversation.

However, if the call is informal (with family, friends, or close colleagues), these principles are usually relaxed.

It must be said that scolding over the phone is very impolite and an inappropriate way of providing an explanation or correction.

To me honestly isn't a bad thing, why because the person calling is the one in need of hearing from you, and call so he /she has to speak at first. That's my own policy anyways

The receiver "answers" to show that they have received the call. Then you the caller have to now state the reason for the call and the synchronous communication progresses.

Sometimes, you do not even know if the call was picked inadvertently and you are just speaking to yourself. Their "hello" or "hi" on the other end of the line signifies their audience and reception of the call.

In fact, clicking the receive button and keeping mute is a sign of disapproval of the call at that time.