Business phone systems, VoIP & contact centers

Three decisions, usually sold as one

The platform is where the call control lives: a hosted service, a system in your own building, or a hybrid where some sites are hosted and others are not. The connectivity is the path the calls take — over the internet, over a dedicated circuit, or over traditional lines kept for specific purposes. The numbers and features are what staff and customers experience: direct numbers, main numbers, queues, voicemail, recording, and the integrations into whatever system holds the customer relationship. They are sold together because bundling is convenient, and that convenience is exactly what makes a later change expensive. Ask for the three parts priced and described separately even if you buy them from one supplier, because that is the only version of the proposal in which you can see what you are choosing.

• Platform: hosted, on-premises, or a mix across sites.
• Connectivity: internet path, dedicated circuit, or retained lines.
• Numbers and features: what staff and callers actually touch.
• Integrations: the systems that must receive or place calls.

Unified communications reprices the line as a person

Standalone hosted telephony is often priced by the line: a number, an extension, a desk phone or a concurrent call channel. Unified communications reprices it by person. A UC subscription assigns one identity a bundle of calling, messaging, presence and meetings, and the public telephone side is usually layered on separately, so a seat can exist without a calling plan and a calling plan can be added to a seat that already existed. That has three consequences for a quote. The billable object moves from the device on the desk to the person sitting at it, so one person using a desk phone and a softphone is normally one seat, while a shared phone in a corridor is still a licence. A base collaboration entitlement is not a statement that anyone can make an external call, because PSTN calling is an add-on. And the entitlement split means the polite question to a supplier is not what the platform costs but which of the three parts of the estate each price line covers.

• Standalone VoIP prices the line; unified communications prices the person behind it.
• PSTN calling is usually a separate calling plan, not part of the base seat.
• One person on two devices is normally one seat; one shared phone is still a licence.
• Ask which part of the estate each price line covers, not just the platform.

Licensing is per seat, so roles decide the count

Most phone platforms licence per named user, which turns a headcount into a recurring commitment and makes the role breakdown the most valuable document in the project. Separate the people who need a direct number from the people who only need to be reachable, and separate both from the places that need a device but not a person — a lobby handset, a warehouse phone, a door entry point. Those common-area devices are commonly licensed differently, and treating them as users is one of the most frequent sources of an inflated quote. Then count the roles that need features beyond calling: queues, recording, supervisor dashboards, and integration with the customer system. Feature tiers are usually what actually separates the offers you receive.

• Users with a direct number, users reachable only, and devices with neither.
• Common-area and shared devices as their own line item.
• Roles needing queues, recording or supervisor access.
• Expected joiners and leavers over the commitment term.

Extensions that are not people: resource accounts and shared devices

A voice deployment bills more than the people who use it. In Microsoft Teams every auto attendant and every call queue needs a resource account, and each resource account requires its own licence — an allocation is included with Teams Phone subscriptions and further licences can be obtained — and the account is deliberately disabled for sign-in, so it can never appear on a headcount. Resource accounts can be given toll or toll-free numbers, so the single main number that answers and routes calls is itself a licensed object rather than a service feature. Beyond them sit the common-area phones in lobbies, warehouses and meeting rooms, and the analog devices that outlive every office move: fax lines, lift phones, alarm panels and door entry. These follow their own licensing rules and their own emergency-calling configuration, and a device that is never signed in still needs a correct dispatchable location. Build the licence count from the device inventory rather than from the staff list, and re-check it whenever a site adds a queue or a lobby phone.

• Each auto attendant and each call queue needs a resource account and a licence.
• Resource accounts are disabled for sign-in, so they never appear on a staff list.
• Common-area phones and analog lines carry their own licences and their own emergency addresses.
• Reconcile the licence count against the device inventory, not the payroll.

Emergency calling is an obligation, not a feature

For multi-line telephone systems, emergency calling carries regulatory duties rather than being a checkbox on a feature list. The rules require that a caller can reach emergency services directly without an access code, that a notification goes to a central point on site, and that the location information passed with the call is specific enough to find the person — a street address alone does not identify a floor or a suite. Those duties land on the system and on the organisation operating it, and they apply to the whole estate, including sites added after the original deployment and users who take their phone home. Ask the supplier to show how a dispatchable location is set for each device and how notifications are tested, then test it yourself once per site and keep the record.

• Direct emergency calling with no access code.
• Notification to a monitored point on site, not only to a mailbox.
• A location specific enough to find the caller inside the building.
• A test performed once per site, with the result kept on file.

The circuit carries the media, so it has to be sized and marked

Hosting moves the call control off site but leaves the media on the local circuit, so the connectivity is voice infrastructure and has to be sized and marked like it. Bandwidth arithmetic starts from the payload rather than the codec headline. G.711 carries a 160-byte payload in each 20-millisecond packet, and every packet also carries an RTP, UDP and IP header of 40 bytes, so the header adds roughly a quarter on top of the payload and the real per-call rate is higher than the codec's nominal figure. Compressed codecs shrink the payload, which makes that fixed header a larger share of each packet rather than a smaller one, and shorter packetisation intervals send more packets per second and raise the overhead again. Capacity is only half of it. Quality of service marks voice into a priority queue using DSCP values and port-based access control lists; for Microsoft Teams the published markings are 46 (Expedited Forwarding) for audio, 34 for video, 18 for application and screen sharing, and 40 for signalling. The three qualities to protect are the ones the same guidance names — jitter, packet loss and delayed round-trip time — and the requirement should say where each is measured and over what period, because a target without a measurement point is not a specification.

• Size the circuit on payload plus the 40-byte RTP/UDP/IP header, not the codec rate alone.
• Compressed codecs make the fixed packet header a larger proportion, not a smaller one.
• Shorter packetisation means more packets a second and more overhead.
• Write the quality requirement with a measurement point, a period and a percentile.

Number porting is a project with documents

Porting is governed by numbering rules and it fails for administrative reasons far more often than technical ones: a letter of authorisation signed by someone the losing carrier does not recognise, a billing account number typed with the wrong separator, a PIN nobody wrote down, a number that appears on one invoice but is billed under another entity. The defence is an inventory built before the move — every number, what it is used for, which invoice it appears on, and which system answers it. Then decide the order of movement, because main numbers, emergency services numbers and numbers printed on signage or vehicles are poor candidates for a first attempt. Port in a batch you can watch, confirm the calls arrive, and only then schedule the next.

• An inventory of every number and what it is used for.
• The invoice, account number and PIN for each losing carrier.
• A porting order that starts with numbers that can safely fail.
• Confirmation calls placed after each batch, before the next one.

Caller authentication and text registration travel with the system

Outbound calling and outbound texting both carry registration duties that sit with the business rather than only with the supplier. Carriers use caller identity authentication to verify that a call from a number is genuinely from that number, and calls that cannot be verified are more likely to be labelled or blocked. Business texting is registered separately, by brand and campaign, and an unregistered sender can see messages filtered before they reach the customer. Both are recoverable situations, but they take days or weeks rather than hours, and they are miserable to discover during a campaign. Establish before cutover who holds the registration, which legal entity it names, and what happens to it if you change supplier.

• Who holds the caller-identity attestation for your numbers.
• Which entity and campaign the text registration names.
• What happens to both if you change supplier.
• A test message and test call to a known handset before launch.

What to gather before asking for pricing

Quotes improve sharply when the request carries the estate. Bring a number inventory with each number's purpose, a user list split by role and whether a direct number is needed, a list of sites with their connectivity and how many devices sit at each, the business systems the phone platform must integrate with, and the call flows that matter — what happens after hours, during peak, and when nobody answers. Add the constraints that are easy to forget: recording obligations, industry rules that apply to your calls, whether staff take calls on personal devices, and whether any site has connectivity good enough to carry voice at all.

• Numbers by purpose, users by role, sites by device count.
• Systems the platform must integrate with, by name.
• Call flows for peak, after hours and no-answer.
• Any recording, industry or consent obligation that applies.

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