whether this is correct from the point of view of a native speaker It's reasonable advice, but you can add Mr if you want. It's a matter of local customs rather than a matter of grammar. Where I used to work, we usually answered the phone in one of these two ways: .
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???whether this is correct from the point of view of a native speakerIt's reasonable advice, but you can add Mr if you want. It's a matter of local customs rather than a matter of grammar.
???Then, say in an office or in the military, can I say one of these?"Hello, Sales Manager David Kim speaking.""Hello, Lieutenant David Kim Sepaking."For the office, your suggestion is fine, though it is common to omit "hello" and/or "speaking". For the military, I imagine that stating your rank is usual, but your commanding officer should be the source of y