Either of the above is good, possibly adding "John Smith speaking" to a) or substituing "John Smith" for the company name in b)
If it's a receptionist, then eliminate the person's name and it's still good. A little long winded, but OK.
Gack! This is just begging for smartass answers and comments from customers. Some management school hotshot learned that the language used and phrases spoken by employees can affect tone and professionalism of a transaction, but didn't quite get the real idea. Being polite and professional is good, over-reaching into smarmy is bad.
Bill Ranck Blacksburg, Va.