Numbers & carriers

Hosted PBX: the phone system without the cabinet

Reviewed by Sujan ThapaliyaLast updated August 18, 2026

What is a hosted pbx?

A hosted PBX is a business phone system that runs as software in a provider's data centre instead of a box on your premises. Handsets and softphones register to it over the internet, and capacity, extensions and numbers change in configuration rather than by an engineer visit.

Why hosted pbx works better on numbers you own: on a shared pool your calls are a small fraction of the traffic from the same block, so the caller-ID reputation is mostly other businesses' calling and signing caps at B attestation. On owned numbers the reputation is your own, callbacks reach your team, and calls sign at A attestation with CNAM registered. — Hosted PBX runs on numbers you own outright, which is what the diagram's right-hand column describes.

How it works

Hosted PBX in four steps

No implementation project. Most teams are dialling the same day they sign up.

1
Bring or buy the numbers
Port the numbers you already publish, or provision new ones. Either way they are yours, which is what makes caller identity and attestation work properly later.
2
Create users and extensions
Each person gets an extension and, where it helps, a direct number. Softphones register instantly; desk phones can be provisioned from the same configuration.
3
Build the call flow
Auto attendant, hours, hunt groups or queues, voicemail, and the fallbacks for each. This is the part that decides whether the system feels professional.
4
Cut over and keep the old route live
Point the numbers when the flow is tested. Porting keeps them ringing throughout, so there is no window where customers reach nothing.

Capabilities

What you get

No hardware to maintain

No cabinet, no cards, no maintenance contract, and no engineer visit to add a line. Capacity is a configuration change.

Works wherever people are

Remote staff are ordinary extensions rather than a forwarding rule, so transfers, hold and presence behave the same at home as in the office.

Desk phones or softphones

Provision handsets where a physical phone is the right tool — reception, warehouse, clinical — and softphones everywhere else.

Numbers you own

Numbers are provisioned to you rather than drawn from a shared pool, which is what allows a registered business name and full attestation on outbound calls.

Usage pricing

No per-seat licence. Numbers carry a monthly rental and calls are billed per minute, which is what makes occasional users effectively free.

Dialing and AI on the same system

The outbound dialer, AI voice agents, recording and messaging run on the same numbers and the same wallet rather than as a second platform.

Hosted or on-premises: what actually decides it

The remaining argument for on-premises is regulatory or connectivity constraint, not capability.
	Hosted PBX	On-premises PBX
Adding capacity	A configuration change	Hardware, and often an engineer
Cost shape	Operating cost, scales with use	Capital cost, plus maintenance
Remote staff	Ordinary extensions	VPN or forwarding, with the quirks that brings
Site outage	System keeps running; calls reroute	System is in the building
Upgrades	Continuous, by the provider	Projects, scheduled and paid for
Control	Configuration, within what the platform allows	Total, including total responsibility

The ISDN switch-off is the forcing function

Traditional digital lines are being withdrawn on national timetables that have already passed in some countries and are approaching in others. Businesses still on ISDN or a PRI face a migration whether they planned one or not, and the ones who plan it choose their replacement while the ones who do not take whatever is available at the deadline.

There are two honest paths. Keep the PBX and replace the lines with a SIP trunk, which is the smaller change and right when the system still suits you. Or move the system itself, which is right when the phone system is already the thing people complain about. Both keep your numbers.

Fit

Who a hosted pbx is right for

If none of these describe you, a different mode probably fits better; the comparison pages lay out the trade-offs honestly.

Businesses still running an on-premises PBX facing an ISDN switch-off
Teams with staff in more than one location
Offices where half the seats barely use the phone and a per-seat licence wastes money
Anyone who needs a new line today rather than after a site visit

Frequently asked questions

What is the difference between a hosted PBX and a SIP trunk?

A hosted PBX replaces the phone system itself. A SIP trunk replaces only the lines behind a PBX you keep. If your existing system works and you are losing ISDN, a trunk is the smaller change; if the system is the problem, hosting it is the answer.

Do I need special phones?

No. Softphones run on the computers and mobiles people already have. IP desk phones work where a physical handset matters, and most current models can be provisioned automatically.

What happens if the internet goes down?

Calls fail over to whatever you configured — mobiles, another site, or voicemail — because the system itself is not on your premises. That is a meaningful advantage over an on-premises PBX, which goes down with the building.

Can I keep my numbers?

Yes. Numbers are portable and porting keeps them ringing throughout the move. A provider that makes porting out difficult is telling you what leaving will look like.

Sources

ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.
North American Numbering Plan Administrator — NANPAArea code assignments, relief planning, and which codes are in service across the North American Numbering Plan.
Combating Spoofed Robocalls with Caller ID Authentication — Federal Communications CommissionThe STIR/SHAKEN framework, the attestation levels carriers sign calls with, and the mandate requiring providers to authenticate caller ID.

Try hosted pbx without a contract

No seat licences, no minimum commitment. Add a number, top up a wallet, and start. Release the number whenever you like; your remaining balance stays yours.

No subscription
Owned numbers with Attestation A
Compliance built in

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