Our AI Agents Answer the Phone Now. Here's What a Minute Costs.
· 4 min · sphinxagent.ai
For most of this year, a Sphinx Agent lived mostly in a chat bubble on someone's website. That covers a lot of customer questions. It doesn't cover the plumber whose customers would rather call than type, or the bakery that gets the same "are you open Sunday?" call twenty times a week.
As of today, the Pro plan comes with a real US phone number that your agent answers. Same agent, same knowledge base, same custom answers you already set up for the website. A caller dials the number and your agent picks up.
What happens on a call
The agent answers using whatever it knows right now: your knowledge base, your custom answers and your instructions. If you edit an answer at 2 p.m., the 2:05 caller gets the new one. You pick the voice when you set up the agent.
When the call ends, three things happen:
- The full transcript shows up in Conversations. There's a new Phone filter so calls don't get buried under website chats.
- The caller's number is added to your Leads, next to the leads from web chat, and exportable to CSV the same way.
- You get an email, so you don't have to sit in the dashboard waiting for something to happen.
What it can't do (yet)
Worth knowing before you turn it on: the phone agent can't transfer a caller to a human, book into your calendar, take a payment or place outbound calls. It answers questions and takes down who called. That's the job for now.
There are also two limits built in on purpose. An account handles one call at a time; a second caller hears that the line is busy. And a single call stops at 10 minutes, or sooner if your monthly minutes run out. Both limits are there so a stuck call or a prank caller can't eat your whole month.
The plan and the minutes
Pro is $49 a month (or $490 a year) and includes one phone line with 60 call minutes a month, shared across the account and reset on the 1st. When the minutes are used up, new callers hear a short message instead of reaching the agent, and a call in progress ends when the account's minutes do. Free and Starter don't include a phone line. Browser voice chat on the website is still on every plan, including Free.
What a minute actually costs us
I measured this before deciding how many minutes to include, because voice AI pricing is all over the place. A call goes through four services: one for the phone line itself, one that turns the caller's speech into text, the language model that writes the reply (Claude Haiku on calls), and one that turns the reply back into a voice.
Added up on real test calls, it comes to about ten cents a minute. A 23-second test call cost just under four cents. So 60 minutes is roughly $6 of the $49 Pro price, which leaves room for the other things Pro includes without the plan losing money on a busy month.
The rest of the November cleanup
Shipping voice turned into a full audit of the product, and I found things I wasn't proud of. Fixed this week:
- New agents were silently dropping their knowledge base when you created them, and custom answers were never saved at all. Both are saved now. If you set up an agent before November and it seemed to ignore what you told it, this was why. Open the agent and check its answers.
- The Conversations page was always empty. It was calling something that didn't exist. It works now.
- Checkout failed for anyone who arrived through a referral link. Fixed.
- Deleting your account failed after cancelling a subscription. Fixed.
- Every agent now runs on Claude Haiku 4.5 by default. The setup wizard has a real model picker, and Pro unlocks Claude Sonnet and GPT-4o. Typed chat messages go only to Anthropic and OpenAI now (Gemini and DeepSeek are gone). Phone calls also pass through the phone, speech-to-text and voice services described above.
If you run a small business and you've been meaning to put something on your website that answers questions after hours, the Free plan gives you one agent and 100 replies a month to try it. If you want it answering the phone, that's Pro.
Wondering how this compares with ChatWit, our other AI receptionist? I wrote that up separately: ChatWit or Sphinx Agent?
Questions or feedback? Email tk@snapitsaas.com.