Which is correct when answering a business phone:
Good Morning, Jane Smith's office, Cindy speaking
Good Morning, Jane Smith's office, this is Cindy
Either one is fine.
Whichever one Jane Smith prefers for you to answer the phone is the better choice.
When Jane answers, does she say "This is Jane"? (That's what I say. Company name marketing. This is Barb.) Or does she pick up and say "Jane Smith speaking"?