Can the AI answer only when the business owner or receptionist does not pick up?

Yes, this is very common. Many businesses prefer a person to answer first, or already have a receptionist, and the AI backs them up so no call is missed.

In the agent's workflow, add a Call forwarding step that tries the owner or receptionist first, for example during business hours, Monday to Friday, nine to five. If nobody answers, the call goes down the no answer branch and the AI takes over, saying what you set. Outside business hours the AI can answer directly.

Another option is conditional call forwarding on the business's phone. Most cell phone providers have codes you can dial so that when the phone is busy or not answered, the call forwards to your AI agent's phone number instead of voicemail.