A front desk is one person, and the phone rings while that person is doing the other nine parts of the job. Most callers who hit voicemail don't leave one — they ring the next practice. Nobody did anything wrong; there was one pair of hands.
The usual answer is a second receptionist, or a temp when the first one is off. That's a wage, a roster, and someone who has to learn the system before they can take a call. Giday is the other answer: it already knows your hours, your services, your people and your diary, and it only takes the calls your receptionist can't.