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Half an hour. We build a flow for your enquiries and run it against your number.
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Resources / Comparisons / Retell, Vapi and Bland
Unibound vs building on Retell, Vapi or Bland.
Retell, Vapi and Bland give a developer an AI voice by the minute. Unibound is the finished system around the voice: every channel, the follow-up, the rules, the inbox and your team's calls. Their headline minute is lower, before the phone line and the voice are added. Unibound is ready to use.
Channels, flows and people, side by side
Three things set these apart: which channels each covers, whether one flow joins them, and whether your own team can work in it.
| Retell, Vapi and Bland | Unibound | |
|---|---|---|
| Built for | Developers and agencies | Firms that want the finished system |
| AI phone calls | In and out, at all three | In and out. Calls nobody answers are free |
| SMS | US numbers only at Retell. Only when the customer texts first at Vapi. Enterprise or Agent Phone plan at Bland | Yes: sent by a flow, written by AI, and two-way |
| Not offered as a channel by any of the three | Yes, on your own WhatsApp business account | |
| Not offered by any of the three | Yes, from your own domain | |
| Web chat | A chat widget at all three | Yes, a widget for your website |
| A flow across channels | Retell's Dialer runs calls and texts over days. Vapi and Bland design one conversation at a time | Yes. Calls, messages, waits and people are steps, and each result has its own next step |
| Your team makes and takes calls in it | No. Calls are transferred to a phone number | Yes: browser calls, a call queue, dialling sessions and calls routed to teams |
| A person takes over from the AI | On texts at Bland. Otherwise a call transfer | Yes, in one inbox and one call queue, and can hand back |
| Cost per booking | Not found | Yes. Every flow has a goal and a cost for each contact who reached it |
| Unanswered calls | Not billed at Retell. At least $0.015 an attempt at Bland. Not stated at Vapi | Free |
| Where data is held | The US at Retell. An EU region on Vapi's Premier package and Bland's Enterprise plan | Customer records are stored in London |
| How you pay | By the minute, in dollars, with several line items | A monthly fee plus usage, in pounds |
One call, or everything that follows it
Most leads are not won on the first call. They are won on the text after a missed call, the call back at the time they asked for, the answer to a question two days later. These platforms are built around the call. Retell has gone furthest: its Dialer runs a sequence of calls and texts over several days. Its texts work on US numbers only, and none of the three offers WhatsApp, email, or a place for your team to make calls.
In Unibound every step ends in a result, and each result leads to its own next step, on whichever channel fits. You draw that once and it runs for every contact.
| What happened | What Unibound does next |
|---|---|
| They answer and want to go ahead | Books the appointment and stops the chasing |
| They ask to be called later | Waits until the time they asked for, then rings again |
| Nobody answers | Sends a WhatsApp or text, waits for a reply, and tries again the next morning |
| They reply with a question | The AI answers from your own material, on the channel they used |
| They ask for a person | Puts them in your team's queue with the whole history |
| They say no, or opt out | Stops, on every channel |
The problem you are trying to fix
Most firms looking at these tools have the same few problems. This is what each does about them.
| The problem | On a developer platform | With Unibound |
|---|---|---|
| New enquiries wait until someone is free | Your developer connects the form to the platform. Retell's Dialer can then ring and retry on a schedule; Vapi's campaigns run once. | Point your form or CRM at a flow. It rings within seconds, then follows up on other channels. |
| Most people answer a message before a call | Texts are for US numbers at Retell, inbound-led at Vapi, and on Bland's Enterprise or Agent Phone plans. None offers WhatsApp or email. | The flow moves to WhatsApp, text or email after a missed call and waits for a reply. |
| One wrong call could cost you a fine | Retell checks an opt-out list before each call. Vapi has no built-in list. Local calling hours are worked out for US and Canadian numbers at Retell and set once per campaign at Vapi. | Opt-outs, calling hours in the contact's own time zone, daily limits and spend are checked before every call and message. |
| Your team needs to step in | The call is transferred to a phone number. Bland's inbox lets a person take over a text conversation. | Your team has an inbox, a call queue and browser calls, and can take over and hand back. |
What each costs
| Published price | |
|---|---|
| Retell | $0.055 a minute for voice infrastructure, plus the voice (from $0.015), the language model and telephony |
| Vapi | $0.05 a minute for hosting, plus speech, language model and voice at cost. Plans from $29 a month; Pro has a $999 a month minimum |
| Bland | $0.14 a minute, or $0.12 with the $299 a month Build plan. Telephony is billed separately |
| Unibound | 16p a started minute with the line and the AI included, with no monthly fee on pay as you go for one user |
For 450 AI minutes a month, with a UK phone line, the bill on these platforms is about £40 to £75 depending on the voice and model, and Unibound's is £72, with no monthly fee on pay as you go for one user. What decides it is everything around the calls: the other channels, the rules and your team's side, which you build or do without.
Checked on Prices and features come from each company's own pages, listed under Sources. Prices exclude VAT. Where we say something was not found, we looked on those pages and did not see it; products change, so check before you decide.
Which suits you
Retell, Vapi and Bland are the better choice if
- You have developers and want to own every part
- Voice is one feature inside your own product
- You will run very high volumes where a few pence a minute decides it
Unibound is the better choice if
- You need WhatsApp and email around the calls, on UK numbers
- Your own people must make and take calls alongside the AI
- Nobody on your team writes code
- You want the calling rules handled for you
Questions people ask
Is Unibound built on Retell or Vapi?
No. Unibound runs its own voice service on OpenAI's voice model and Twilio phone lines.
How does Unibound's 16p a minute compare?
The 16p includes the UK phone line, the AI, the transcript, the recording and the summary, and you pay nothing when nobody answers. These platforms price each part separately: with a UK line added, a minute comes to roughly 9p to 17p depending on the voice and model. Unibound bills by the started minute and they bill by the second, so very short calls cost less with them.
Can these platforms text or WhatsApp a UK customer after a missed call?
Not from what their own pages say. Retell's SMS works on US numbers, Vapi's assistants cannot send the first message, and Bland's SMS is for US numbers on its Enterprise or Agent Phone plans. None lists WhatsApp or email as a channel.
An agency offered to build this on Retell for less. What should I ask?
Ask how a UK customer gets a message after a missed call, where your team picks up a conversation, how opt-outs and calling hours are enforced, and who makes changes.
Sources
- Retell AI, pricing. retellai.com
- Retell AI docs, Dialer. docs.retellai.com
- Retell AI docs, SMS. docs.retellai.com
- Vapi, pricing. vapi.ai
- Vapi docs, SMS chat. docs.vapi.ai
- Vapi docs, outbound campaigns. docs.vapi.ai
- Vapi docs, EU region. docs.vapi.ai
- Bland AI, pricing. bland.ai
- Bland AI docs, billing. docs.bland.ai
- Bland AI docs, SMS. docs.bland.ai
- Twilio, UK voice pricing. twilio.com
- Unibound, pricing. unibound.ai
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