1) Answering the phone and forgetting which company they work for and/or the company greeting and having to pause to remember it.
2) Answering the phone then continuing a conversation with a colleague.
3) Answering the phone while still laughing at a joke with a colleague.
4) Shouting “HELLO??” if you pause for a second or two while thinking about a question they have asked you or a new piece of information they have given you.