Moving to IP telephony: what really changes for an SMB

Moving to IP telephony means replacing the old phone system (PBX) and its lines with a SIP trunk and a software phone system, hosted or installed on your premises. You keep your numbers, internal calls between sites no longer go through the carrier, and every employee can answer from a desk phone, a computer or a mobile. The key to success is not the software, it is the network. The traditional phone system is often the last “legacy” piece of equipment in an SMB: it works, so nobody touches it, until the day you need to add an extension, open a site or let a team work remotely. Here is what a migration really brings, and how to run it without dropping a single call.

What goes down: the bill and the lock-in

Calls travel over your internet access and a SIP trunk supplied by a carrier. Several cost items disappear or shrink:

• Internal calls between sites travel over your network and are no longer billed by the carrier.
• Per-line subscriptions are replaced by SIP channels, adjusted to the number of simultaneous calls you actually need.
• Maintenance of a proprietary PBX, often tied to a single provider, disappears.
• Hardware is limited to IP handsets for those who need them, and an app for everyone else.

The real saving depends on your situation: number of sites, call volume, licences chosen. Always compare quotes on full three-year cost, licences, handsets, trunk and maintenance included, not just on purchase price.

What stays: your numbers

Number porting lets you keep your existing numbers, including short or special numbers depending on what the carrier offers. During the transition, the old and new systems coexist: calls land on one, then on the other at switchover time, with no interruption for your customers.

What you gain: features

• Mobile and desktop apps: your business number follows you, working from home or on the road.
• Call queues and IVR menus: reception is structured, calls no longer get lost.
• Office hours and automatic forwarding: the system switches itself to closed, holiday or on-call mode.
• Recording and statistics: essential for customer service or appointment booking.
• CRM integration: the customer’s record opens when they call.
• Additional channels: depending on the solution, video meetings, web chat or messaging, as explained in WhatsApp Business and 3CX.

	Traditional PBX	IP telephony
Lines	Physical lines per channel	SIP trunk, adjustable channels
Calls between sites	Billed by the carrier	Over your network
Remote work	Limited call forwarding	Full mobile and desktop apps
Adding an extension	Hardware card or module	Licence plus IP handset or app
Monitoring	Rarely	Statistics, recordings, alerts
Evolution	Tied to the PBX vendor	Regular software updates

What to prepare: the network

Call quality depends on the network, not the phone system. A successful migration rests on a few simple but essential settings:

• A voice VLAN separating telephony from workstations.
• QoS prioritisation on the firewall and switches, so voice goes ahead of downloads.
• PoE switches to power IP handsets without mains adapters.
• A backup link: a second fiber or 4G, and for multi-site companies an SD-WAN that fails over automatically, see FortiGate multi-site SD-WAN.
• WiFi, if staff make calls from laptops: coverage and roaming must be checked.

That is what separates a successful migration from a painful one. The most common problems, choppy voice, dropped calls, echo, are covered in IP telephony: 10 mistakes that hurt call quality.

Hosted or on premises?

A hosted phone system does not depend on your office: if the building is inaccessible or offline, staff keep answering from the mobile app. An on-premises system, as an appliance or a virtual server, suits companies that want to keep everything in-house or already have a reliable server room. Either way, configuration backup and monitoring are part of the deployment.

Special cases: fax, alarms, door entry

A PBX often connects much more than phones. Before switchover, every device plugged into an analogue line must be identified:

• Fax machines, still used by some administrations and partners: they can be replaced by a fax-to-email service or kept on an analogue gateway.
• Alarm diallers and lift lines, which must keep calling their monitoring centre. They often stay on a dedicated line or a gateway tested with the relevant provider.
• Door entry systems and intercoms, which can be integrated into the IP phone system to open the door from a handset or the app.
• Older payment terminals, which sometimes still use a phone line.

These devices are rarely documented, and they are the ones that cause trouble the day after migration.

Securing the phone system

An IP phone system is a server exposed to the internet and must be protected as such. Strong passwords on every extension and account, restricted admin access, limits on international calls, regular updates and firewall filtering prevent toll fraud, where attackers route expensive calls through a poorly protected system. These settings are part of every deployment we deliver.

3CX or Yeastar?

3CX is a feature-rich software phone system, hosted or on premises. Yeastar P-Series is a robust appliance, simple to administer, popular with clinics and industrial sites. We deploy both and guide you based on your usage; the full comparison is in 3CX vs Yeastar vs Teams Phone, and how 3CX works in 3CX: the phone system for SMBs.

Steps for a migration without downtime

1. Inventory: numbers, extensions, ring groups, IVR menus, forwarding, any fax lines, carrier contracts and their end dates.
2. Network audit: switches, PoE, firewall, internet links, WiFi.
3. Numbering plan and call flows designed and validated with the team that answers the phone.
4. Preparation: voice VLAN, QoS, SIP trunk, installation of the system and handsets.
5. Testing with a pilot group on temporary numbers.
6. Switchover: number porting, coexistence with the old system, call-by-call checks.
7. Short training for users and reception, then removal of the old PBX.

Mistakes to avoid

1. Migrating without a voice VLAN or QoS, then blaming the software for poor quality.
2. Forgetting numbers or special lines (alarm, lift, fax) in the inventory.
3. Cancelling old lines before porting is confirmed.
4. Copying an IVR menu that no longer makes sense instead of rethinking reception.
5. Providing no backup link for an on-premises system.
6. Not training reception, left alone with new features.

Checklist before launching the migration

• Full inventory of numbers, extensions and call flows.
• Carrier contracts reviewed, cancellation dates noted.
• PoE switches and voice VLAN ready.
• QoS configured on the firewall.
• Backup link available.
• Hosted or on-premises decision made.
• Dated switchover plan, with a rollback option.
• Training planned for reception and users.

How we do it

We start with an audit of your lines, usage and network, then propose a solution costed over three years. Our team prepares the network, installs the phone system, handles porting with the carrier and is on hand on switchover day. After that, telephony is monitored 24/7 like the rest of your infrastructure, with critical incidents handled in under 15 minutes. Full details are on our IP telephony page, and project examples, without client names, in our case studies.

Is your phone system reaching end of life, or are you opening a new site? The initial audit is free: contact us, we reply within 24 business hours.