This guide is written for telecom, IT and operations buyers sourcing numbers for phone systems, contact centres, and communication platforms — not for consumers picking a second-line app. A DID (Direct Inward Dialing) number, also called a virtual number, is a public phone number provisioned online and delivered to you over SIP (Session Initiation Protocol — the signalling standard for internet calls). If those terms are new, start with what a DID number is.
Most "best DID provider" lists are written by vendors ranking themselves first. That is why this is a checklist, not a ranking: a set of criteria you score any provider against, including the one you already use. Where it helps, Temptera is used as a worked example of how to apply a criterion — not as the answer to it.
On this page
Does the provider cover your countries and number types?
Coverage is the first filter because nothing else matters if the numbers you need are not in stock. Check the specific countries you operate in and the specific types you need — local (geographic, tied to a city prefix), national (non-geographic, countrywide), toll-free (free to the caller), and mobile-range — not just a headline country count. A provider can advertise 100+ countries and still lack the one national number or toll-free range you need.
What good looks like: live, per-country inventory you can see before buying, with the number types available in each market shown clearly. What to ask any provider: is the exact number I want in stock today in this country, and which types are available here? For example, Temptera exposes live per-country availability in the coverage table and portal, so you confirm stock before committing.
How does the provider handle documentation and KYC?
Regulators allocate number ranges to licensed carriers and attach verification requirements to those ranges, so KYC (Know Your Customer — identity and eligibility checks) is a fact of buying numbers, not a provider quirk. Requirements vary by country and number type and typically fall into classes: none, ID only, ID plus proof of address, or evidence of local presence. What separates providers is whether they tell you the requirement before you order and how much friction the process adds.
What good looks like: the documentation class is stated on the number at order time, uploads are handled in the portal, and undocumented markets activate immediately. What to ask: what will you need from me to activate this specific number, and how long does verification take in this country?
Is SIP delivery and audio quality solid?
A number is only as good as the call path behind it. Inbound calls arrive as a SIP INVITE — the request that sets up a call — carrying the dialled number to your PBX (Private Branch Exchange, your call-switching system) or softswitch. Delivery quality depends on codec support, how close the provider's switching is to the origin, and whether there is a failover path if your primary endpoint is unreachable.
What good looks like: standard codec support (such as G.711 and G.729), IP or credential-based trunk authentication, geographically distributed switching for lower latency, and configurable failover destinations. What to ask: which codecs do you support, where does my traffic switch, and can I set a backup route? See how this connects in SIP trunking.
Can you port numbers in — and out?
Porting is moving an existing number between providers while keeping the number itself. Two things matter: can the provider bring your current numbers in, and — just as important — will it let you take numbers out if you leave. Providers that make porting out difficult are relying on friction to keep you.
What good looks like: a documented porting process both ways, realistic timelines quoted up front, and no penalty for porting away. What to ask: can you port my existing numbers in these countries, and what is your process and timeline for porting out?
Which billing model fits your traffic?
There is no universally "cheaper" model — there is the one that fits your volume. The three common shapes are consumption-based (pay per number and per minute used, no minimums), subscription (a fixed monthly fee for a bundle), and minimum-commit (a floor you pay whether or not you use it). Judge each against your real usage, not the advertised rate.
| Model | How you pay | Suits | Watch for |
|---|---|---|---|
| Consumption-based | Per number and per minute actually used; no minimums. | Variable, seasonal or growing volume; testing new markets. | Per-unit rates can be higher than a committed bundle. |
| Subscription | Fixed monthly fee for a set bundle of numbers or minutes. | High, predictable volume you can budget confidently. | Paying for unused capacity in quiet months. |
| Minimum-commit | A spend floor plus usage above it. | Large, stable buyers negotiating a lower unit rate. | The floor is sunk cost if volume drops. |
Temptera uses a consumption-based model with no monthly minimums and no lock-ins; live per-route rates appear once you create an account. That fits variable volume — a high, steady buyer should still compare it against a committed bundle. See the pricing model for how consumption billing works here.
How fast is provisioning and support?
Provisioning speed sets how quickly you can act. Self-serve providers let you buy and connect a number in minutes; sales-gated ones add days before you have anything live. Support quality shows up when a route breaks, a port stalls, or a document is queried — not in the demo.
What good looks like: instant activation for undocumented inventory, a portal that provisions without a sales call, and reachable technical support with clear escalation. What to ask: can I self-serve a number right now, and who do I reach if a live route degrades at 2am?
What are the contract terms and lock-ins?
Read the commitment before the rate. The terms that bind you are the minimum term, the notice period to cancel, and whether numbers stay portable if you leave. None of these are automatically disqualifying — a longer term is fine if it buys you something concrete — but they should be explicit.
What good looks like: month-to-month terms with numbers you can port out, or a longer commitment that is clearly priced against a real benefit. What to ask: what is the minimum term, the notice period, and can I keep my numbers if I leave?