The short answer
In the sub-account, go to AI Agents, Voice AI, click Create Agent and pick a marketplace agent, a custom agent or the flow builder. Set the voice, model, prompt and greeting, add a knowledge base and actions such as booking or call transfer, test it with a web call, then assign a phone number on the Deploy tab.
Before you build
You need the View & Manage Voice AI Agents permission, one clear job for the agent (answering questions, booking, qualifying leads or routing calls), approved business information for the prompt or knowledge base, and whatever calendars, workflows or transfer numbers its actions will use. Live calls need an LC Phone number, a Twilio number or a number pool. Billing is pay per use by default: HighLevel lists a $0.045 per minute voice engine, plus $0.015 per minute for OpenAI or Cartesia voices, plus model tokens, with phone minutes on top. AI Employee Growth ($50 a month per sub-account, 100 Voice AI minutes) or Unlimited ($97, fair use) cover the AI part instead.
Outbound calling needs more setup: accepting HighLevel's outbound terms, identity verification and consent language that covers automated calls, and calls go out only between 8 a.m. and 8 p.m. in the contact's time zone, with a cap of 5,000 outbound AI calls per location per day. Rules on AI and automated calls vary by state, so talk to a lawyer about TCPA consent before any outbound campaign.
Build and test the agent
Open AI Agents, Voice AI, Agent List, click + Create Agent and choose Browse Marketplace, Create Custom Agent or Flow Based Builder. In the full-screen builder enter the name, voice, model, language, prompt and welcome message, then save. HighLevel suggests a prompt that states the agent's role, what to collect, what it must not discuss, when each action runs and when to hand off, and that tells it not to guess. Connect a knowledge base for hours, services and policies. Under Actions, add only what the job needs, such as Appointment Booking, Call Transfer, Send SMS, Update Contact Field or Trigger a Workflow. Test with Web Call, then a real Phone Call, because call transfers do not run in a web call.
Deploy it to a phone number
On the agent's Deploy tab, pick a phone number or number pool (you can buy one there), choose Answer Calls Directly or Use as Backup, and set Working Hours to All Hours or a Custom Schedule. Other settings can still divert calls. In Settings, Phone System, open the number's three-dot menu, choose Edit Configuration and check that the Call Forwarding tab shows Voice AI. HighLevel suggests an inbound timeout of 1 to 3 seconds, because a call that reaches local voicemail is marked completed and the agent never picks up. For an agent that takes every call, do not assign the sub-account's default number. Finish with a live call from an outside phone and read the transcript.
More answers in HighLevel questions. For costs, see GoHighLevel pricing or run the cost calculator.