Phone Numbers
Buy a real phone number, then turn on Calls, SMS, and WhatsApp as features on it
A phone number is the unit of telephony on Zernio. You buy (or port in) a real number, and then turn on the capabilities you need on that same number:
- Calls (PSTN voice) - on by default on every number
- SMS (text / MMS) - enable per number (needs an SMS-capable number, plus a carrier registration in the US)
- WhatsApp - connect the number to a WhatsApp Business Account
One number can do all three, or just one. This section covers acquiring and managing the number itself. What you do with it lives in Voice & Calls, SMS, and WhatsApp.
/v1/phone-numbers is the canonical API. The older /v1/whatsapp/phone-numbers/* endpoints are deprecated aliases that still work with the same contracts, kept for existing integrations. New code should use /v1/phone-numbers. There is no separate "WhatsApp number": a WhatsApp number is just a phone number with WhatsApp enabled on it.
Quick Reference
| Property | Value |
|---|---|
| Countries | 54 offerable (see Availability) |
| Default country | United States |
| Pricing | $2 to $25 / month per number, by country (see Availability) |
| Calls (PSTN) | Every number, on by default |
| SMS | Per number (SMS-capable countries only) |
| Connect the number to a WhatsApp Business Account | |
| Get a number | Purchase from inventory, or port one in |
| Number limit | Your plan's profile limit (Unlimited capped at 50) |
Billing model matters
Telephony (Phone Numbers, Voice, SMS) requires the Usage plan with a payment method on file. With that in place:
- All 54 countries are available, and numbers provision inline, no separate checkout. Billing is per number, per month, on your usage-based invoice.
- Calls and SMS features (enabling PSTN voice or SMS on a number) run on the same usage-based plan.
The lifecycle
- See what's available. Availability lists the countries, number types, per-country pricing, and which capabilities each supports.
- Get a number. Purchase one from inventory (with a payment method on file it provisions in the same request, auto-assigned), or port in a number you already own. Regulated countries need a one-time KYC form first.
- Turn on features. Calls are already on. Enable SMS (US numbers need a carrier registration) and/or connect WhatsApp from the number.
- Use it. Place and receive calls, send texts, and read a unified call history across every number and channel.
API conventions
A few patterns hold across all telephony endpoints:
- A number is the unit; features are sub-resources on it. Enable or disable a capability with
POST/DELETEon/v1/phone-numbers/{id}/{feature}(/{id}/voice,/{id}/sms). Call activity lives on its own top-level resources: read call history at/v1/calls, send texts at/v1/sms/messages, place calls at/v1/voice/calls. - State-changing actions read as
POST /resource/{id}/{verb}. When an operation isn't a plain create/read/update/delete it's an explicit action, e.g.POST /v1/voice/calls/{id}/end,/transfer,POST /v1/sms/registrations/{id}/verify-otp,/appeal.
In This Section
Availability & Pricing
Which countries, number types, and capabilities, and what each costs
Buying a Number
Search inventory, purchase, and manage numbers
Porting
Bring an existing number over from another carrier
KYC (Regulated Countries)
Collect identity details where a country requires them
Related Endpoints
- List offerable countries - Live country + pricing + capability list
- Search available numbers - Inventory in a country
- Purchase phone number - Buy a number
- List phone numbers - Every number on your account
- Port numbers in - Transfer from another carrier
- Release phone number - Give a number up
Discord
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Availability & Pricing
Which countries and number types are available, what each costs, and which capabilities they support