CentriWebThe main Synthflow alternatives are Retell AI, Vapi, Bland, ElevenLabs Agents, GoHighLevel’s built-in Voice AI, or a voice agent built and looked after for your business. Which fits comes down to two things: whether you need to start small without an annual contract, and whether your calls have outgrown what a prompt-and-template set-up can manage.
CentriWeb builds and looks after voice agents for clients, on platforms of this kind, so weigh our view with that in mind. We also build many client systems on GoHighLevel. Every fact below comes from each vendor’s own pages, opened in November 2026, in US dollars. Check their page for current prices.
Why people look for Synthflow alternatives now
As at November 2026, Synthflow’s pricing page says every new deployment starts on an annual Enterprise contract. It publishes no per-minute rate, and it says there is no free plan or trial. Pricing is scoped to call volume, phone system, integrations, security needs and launch support.
Its home page describes an enterprise conversational AI platform whose agents answer and make calls for contact centres, BPOs and multi-location brands, with more than 200 integrations and its own telephony. Its documentation describes creating an agent from a prompt, with actions to transfer calls, book meetings and call external APIs.
That is a clear choice of market. For a large contact centre it may be exactly right. For a clinic, a trade business or a five-person office that wants to try an agent on after-hours calls, an annual enterprise agreement is a big first step.
Signs a template-style voice agent has run out of room
Price is one reason to move. The other is that the agent has stopped keeping up with the business. Watch for these:
- Callers ask things it cannot look up. It needs to check a job, a booking or an account in a system it is not connected to.
- One prompt is doing five jobs. New enquiries, existing clients, suppliers and complaints all go through the same instructions, and fixing one breaks another.
- You cannot test a change safely. Every edit goes straight to live callers.
- Locations or brands need different rules. Different hours, services or staff to transfer to.
- You cannot see why a call went wrong. There is a transcript, but no clear record of what the agent tried to do.
- The bill is hard to predict. You cannot tell what next month will cost.
If two or more of these sound familiar, the answer is usually a platform with more control, someone to run it, or both.
Synthflow alternatives compared
| Option | What it is | How it charges (as at Nov 2026) | Who maintains it | Who it suits |
|---|---|---|---|---|
| Retell AI | Platform to build, test, deploy and monitor voice agents | Pay as you go, US$0.07 to US$0.31 a minute | You or a builder; dashboard or API | Businesses wanting no-code and developer options in one |
| Vapi | Developer platform for voice agents | US$0.05 a minute hosting plus providers at cost | A developer or technical partner | Teams that want to choose each part |
| Bland | Voice agent platform with one per-minute rate | US$0.14 a minute on Start; US$0.12 plus US$299 a month on Build | You or a builder | Owners who want one simple rate |
| ElevenLabs Agents | Agents from a voice company | Monthly plans with included minutes, then US$0.08 a minute | You or a builder | Businesses that want a monthly plan |
| GoHighLevel Voice AI | Phone agent inside the HighLevel CRM | Per minute plus tokens and phone, or US$50 to US$97 a month per sub-account | Whoever runs your HighLevel account | Businesses already on HighLevel |
| Built and looked after for you | A custom agent on a voice platform, connected to your systems | Platform usage plus a build and support fee | A partner | Businesses with real call volume and no time to run it |
What each alternative does well
Retell AI
Retell’s documentation says you can build entirely from the dashboard with no code, use a conversation flow builder that splits a call into steps for tighter control, or work through its API and SDKs. It lists CRM sync with GoHighLevel, Salesforce, HubSpot, Dynamics 365 and Zoho. Retell’s pricing is pay as you go with no minimums and US$10 of free credit. Its own numbers are US and Canada only, so Australian businesses connect their own carrier.
Vapi
Vapi calls itself “the developer platform for building voice AI agents”. You choose the speech recognition, model and voice, and its pricing page passes those through at cost on top of US$0.05 a minute. A free start with US$5 credit and a US$29 Core plan make it easy to try. It rewards a technical owner or partner.
Bland
Bland’s pricing page publishes one per-minute rate that covers the model, speech recognition and voice: US$0.14 a minute on the Start plan with no platform fee, or US$0.12 on Build with a US$299 monthly platform fee. Transfer time is billed at a lower rate. That is the simplest bill of the group.
ElevenLabs Agents
ElevenLabs Agents pricing runs on monthly plans with included call minutes, from a free plan with 15 minutes up to US$990 a month for 12,375 minutes, then US$0.08 a minute. Model usage is charged on top, and telephony through your own carrier is billed by that carrier.
GoHighLevel Voice AI
If your CRM is already HighLevel, its built-in agent books into the same calendars and triggers the same workflows. HighLevel’s AI pricing article lists a voice engine fee of US$0.045 a minute plus voice, tokens and phone, or AI Employee plans at US$50 and US$97 a month per sub-account. Our guide to GoHighLevel Voice AI covers it in detail.
How to choose between them
- Start with your calls. Write down the five most common reasons people ring and what has to happen after each.
- Decide who will run it. If nobody on your team will test and check calls every week, choose a platform someone else can maintain for you.
- Match the billing to your volume. Low or uncertain volume suits pay as you go. Steady volume may suit a plan with included minutes.
- Check the phone line. Make sure you can use an Australian or New Zealand number, and price your carrier’s charges.
- Run a real test. Most of these offer free credit or a free plan. Put twenty real call types through it before you commit.
Our comparisons of Retell AI and Synthflow and of the main AI voice agent platforms go further on each.
What to take with you when you switch
Voice agents do not move between platforms with an export button. The agent is rebuilt, so gather what made the old one work before you cancel anything:
- The full instructions and any knowledge base content, copied out word for word.
- A list of every action it takes: transfers, bookings, texts, CRM updates, and where each one goes.
- A sample of real call transcripts, good and bad, to test the new agent against.
- Your phone number arrangements, including who holds the number and how calls are forwarded.
Then run the new agent on a slice of calls, such as after hours, while the old set-up handles the rest. Switch fully once the new one has handled a few weeks of real calls without surprises. Our guide on connecting a voice agent to your CRM and calendar covers the wiring.
Where a system built and looked after for you fits better
A custom agent run by a partner makes sense when calls bring in real money, the agent has to work with your calendar, CRM and job or practice software together, and you want someone watching call quality every week. That is part of our AI services, for clinics and health businesses among others.
It does not suit everyone. If you take a handful of calls a week, if you enjoy setting things up and have the time to check them, or if a standard plan on one of the platforms above does the job, start there. You can always move later, and you will know far more about your calls when you do.