Best Synthflow Alternatives for Agencies in 2026

Synthflow builds AI voice agents that answer and make calls inside a company's phone system. It is now sold only as an annual enterprise agreement, priced after a scoping call. Its pricing page says there is no free plan, no trial and no rate by the minute, and every new deployment starts on an enterprise contract. White-label client workspaces come as part of that agreement. That suits contact centers. Agencies with a few local business clients usually want something they can start this week, without a yearly contract.

Quick comparison

Alternative	Monthly fee	What you get	Best for
Synthflow (for reference)	Annual enterprise agreement	Inbound and outbound voice agents, 200+ integrations, white-label workspaces on your domain	Contact centers, BPOs and multi-location brands
ResellPortal	None. $15, $39 or $99 per client a month	Ready-made AI receptionist for chat, booking and phone, billed per client	Agencies with local business clients
Retell AI	None. $0.07 to $0.31 a minute	Voice agents billed by the minute, one workspace per client, dashboard not rebranded	Developers who will build a client portal on its API
Trillet	From $99, then $0.12 a minute plus telephony	Branded voice AI with 1,000 or 3,000 included minutes	Agencies selling phone answering at steady volume
Stammer.ai	$99 for Pro White Label	Agents you build for chat and voice, with your domain and client wallets	Agencies that want to design each agent
GoHighLevel	$97 to $497, plus AI per sub-account	Voice AI as part of its CRM suite, resale through SaaS mode at $497	Agencies whose clients already use its CRM
Dialzara	Custom partner pricing	Calls in and out, AI texting and web chat, in your brand	Larger agencies and telcos

1ResellPortal

ResellPortal's AI Receptionist is ready to sell the day you switch it on. There is nothing to build. Wholesale per client per month is $15 for AI Chat, $39 for Chat + Booking and $99 for Chat + Booking + Phone, with suggested retail prices of $49, $99 and $199. It reads a business's website in about a minute, books into Google, Outlook or Apple calendars, and answers a local US or Canada number in a natural voice. It transfers calls, screens spam and writes a summary of each call. Normal business calling is unlimited, each call can run up to 15 minutes, and nothing is charged by the minute.

You pay no platform fee and sign no contract. Load a wallet with at least $20, get a $10 bonus on a first deposit of $20 or more, and wholesale is taken only for active clients. Client payments go to your own Stripe or PayPal, and clients log in to a dashboard under your brand and domain. The trade-off: it does not let you design custom call flows or run outbound campaigns, and it only issues US and Canada numbers.

2Retell AI

Retell AI is the nearest thing to building agents yourself on pay-as-you-go terms. Minutes cost $0.07 to $0.31, there is nothing to pay upfront, and Retell recommends a separate workspace for each client. Callers hear your client's name, yet the dashboard keeps Retell's branding, so agencies that need a client portal build it on the API.

3Trillet

Trillet sells branded voice AI to agencies on monthly plans from $99, with no setup fee or contract. The Studio plan bundles 1,000 minutes. Agency bundles 3,000 minutes and lets you open unlimited client workspaces. Past the included minutes you pay $0.12 a minute for AI, and telephony is billed on its own. Clients see your brand and domain, never Trillet.

4Stammer.ai

Stammer.ai is a builder: you design chat and voice agents, then sell them as your product. For $99 a month, Pro White Label gives you 5 of each, with more at $10 a month per agent. Your domain, logo and colors replace Stammer.ai's branding. Clients top up their own wallets, and you decide what they pay for replies, voice minutes and agents.

5GoHighLevel

GoHighLevel offers Voice AI as part of its CRM. The suite costs $97, $297 or $497 a month, and reselling it under your brand requires the $497 plan. AI then costs extra for each sub-account. Its $50 AI Employee plan covers 100 voice minutes a month, its $97 plan is unlimited within fair use, and phone charges come on top.

6Dialzara

Dialzara lets agencies resell inbound calls, outbound calls, AI texting and website chat with their own name, logo and domain. Prices are agreed after you apply through a short form.

When Synthflow is still the right choice

Choose Synthflow if you serve contact centers, BPOs or multi-location brands with heavy call volume. It works inside existing phone systems, keeps customers' current numbers, connects to 200+ business tools, and lets you place each workspace in the US or the EU. It lists SOC 2 Type II, ISO 27001 and a HIPAA BAA, and its agreement can include launch support from its own engineers. For large or regulated deployments, that is worth an annual contract.

Common questions

Does Synthflow still have a free plan or monthly pricing?

No. Synthflow's pricing page says it is sold as an annual enterprise agreement, with no free plan, no trial and no per-minute rate. The price comes from a scoping call.

What is the cheapest Synthflow alternative for agencies?

For an agency with a few clients, ResellPortal costs least to start: no monthly fee, a $20 wallet and $15 to $99 a month wholesale per active client. Retell AI skips the monthly fee too but charges for every minute, at $0.07 to $0.31.

Can I white-label an AI voice agent without an annual contract?

Yes. ResellPortal and Trillet have no contracts, and Stammer.ai's plans are billed monthly.

What should I charge for an AI receptionist with phone answering?

ResellPortal suggests $199 a month for chat, booking and phone, against $99 wholesale, which leaves you $100 a month per client.

Create a free ResellPortal account and turn on the AI Receptionist for your first client.

The best Synthflow alternatives for agencies reselling AI voice agents