This article is part of our AI Front Desk hub. Want help applying it? Talk to eSEOspace.
The hidden costs of AI phone agents are hold time, transfers, add-on features, extra concurrent lines, phone charges and texting fees. None of them appears in a headline per-minute rate.
Each is published by the vendor, if you know where to look. Every fee below was checked against the vendor's documentation on 9 November 2026 and can change.
This article is part of our AI Front Desk guide. It is general information, not legal advice.
Key Takeaways
- Retell bills the entire call, including hold time and silence.
- Bland charges separately for transfer minutes.
- Add-ons such as HIPAA data handling, knowledge bases and extra lines can raise your bill.
- Phone system charges can sit outside the AI price.
- Text messaging has registration fees and per-message costs.
Hold time and silence
Retell's pricing page says billing covers the entire duration of the call, including hold time and silence. It explains that speech-to-text stays active during silence. A caller on hold is billable time.
Calls are tracked to the nearest second, with no rounding per call, according to the same page. That detail helps short calls. Other vendors differ.
Ruby's FAQ says it includes hold time and rounds calls up to the nearest 60-second mark. HighLevel's phone pricing guide says partial minutes round up.
Transfers to a person
Transfers are billed differently from vendor to vendor. Retell's page says "Once the call is transferred, the AI voice agent fee stops." It adds that only the telephony fee continues.
Bland's pricing page charges transfer minutes at $0.05 on Start and $0.04 on Build. If your staff stay on a transferred call for long, include those minutes.
Smith.ai handles live help differently. Its AI Receptionist page says "If the escalation is AI-initiated, there is no fee." Choosing to bring in live agents for other tasks is a per-call add-on.
Spam and short calls
Spam can cost money on some plans. Smith.ai's AI Receptionist page says known robocalls and solicitors are automatically blocked. Other vendors have their own rules, so ask how yours treats spam.
Add-ons
Retell lists Knowledge Base at $0.005 a minute, plus $8.00 a month for each knowledge base beyond the 10 it includes free. PII Removal is $0.01 a minute. AI Quality Assurance is free for the first 100 minutes, then $0.10 a minute.
Vapi's pricing page lists a HIPAA add-on at $2,000 a month. Vapi says that covers eligible data handling and a Business Associate Agreement. Treat any add-on as a contract term, not proof your setup follows the law.
Our HIPAA article covers what to check before patient calls reach any vendor.
Concurrent calls
Concurrency is how many calls can run at once. Retell includes 20 for free, then charges $8 per extra line a month. Vapi charges $10 per extra line a month on top of each package's limit.
Bland's page shows daily caps of 100 calls on Start and 2,000 on Build. Check any cap against your busiest day, not your average.
Phone charges
An AI rate and a phone rate can be two separate things. HighLevel's AI pricing guide says "Note: Phone System charges still apply to all phone calls regardless of plan."
Its phone guide lists inbound US and Canada calls at $0.01165 a minute, plus number rental. Retell lists telephony at $0.015 a minute for listed countries, and says there is no charge for SIP trunking or custom telephony.
Ask each vendor whether its quote includes carrier fees. Vapi's page says some transport fees are charged by the provider, not by Vapi.
Texting after the call
If your agent texts callers, budget for registration. A2P 10DLC is the US system for registering business texting from ordinary numbers. Our guide to A2P 10DLC explains it.
Twilio's own pages give different fees. Twilio's brand registration docs, updated 25 September 2026, list a $4.50 TCR brand fee and $41.50 Standard vetting. Twilio's marketing page lists a $44 one-time brand registration or $4 for low-volume.
Confirm the fee at signup. Other providers set their own figures.
Setup, review and labor
The published prices we checked do not show your own time. Set aside hours to write call rules, connect a calendar, review transcripts and run test calls. We have no industry figure for this, so estimate it from your own team.
Some vendors sell this as a service. Dialzara's pricing page lists a Done for You plan starting at $1,500 or more per month. Our guide to AI agent pricing models covers the wider trade-offs.
Next step
Take your busiest day and an average call, then price it through each vendor's full fee list. If you want help scoping a custom agent, see our AI agent development service.
Frequently asked questions
Are AI phone agents charged by the second or the minute?
It varies. Retell tracks calls to the nearest second. HighLevel's phone guide rounds partial minutes up.
Do I pay when a call is transferred?
It depends on the vendor. Retell's AI fee stops at transfer, though telephony continues. Bland charges a separate rate for transfer minutes.
Is HIPAA extra with AI voice platforms?
Sometimes. Vapi lists a $2,000 monthly HIPAA add-on. Retell's compliance page says there is no additional fee to sign its BAA and DPA.
What fees apply to texting after a call?
Expect registration and per-message costs. Twilio's documentation lists brand fees, and its marketing page shows different figures. Confirm with your provider.
How do I find every fee before signing?
Ask for an itemized quote on your own call volume. Include hold time, transfers, telephony, add-ons and texting.
