Teams already lets people call other Teams users. That is not a phone system. Teams Phone is what connects those users to the public telephone network so a customer can dial a ten-digit number and reach a person, a queue, or a lobby wall set.

Once you decide to do that, you still have three separate design questions: how you connect to the PSTN, who gets a personal number, and whether anyone needs a physical device.

How the calls leave Microsoft

For a firm the size we usually see, the honest options are:

  • Microsoft Calling Plans — Microsoft is the carrier. Simplest. Fine when you are in one country and do not have a carrier contract you are required to keep.
  • Operator Connect — your carrier appears in Teams admin center. Best when you want a named telco and do not want to own a Session Border Controller.
  • Direct Routing — you (or we) run a certified SBC. Use it when analog, fax, a surviving PBX, or a stubborn carrier circuit is still in the building.
  • Teams Phone Mobile — the mobile number and the Teams number are the same. Worth it for people who live on a cell and never sit at a desk.

You can mix them. Headquarters on Operator Connect and a warehouse analog gate on Direct Routing is a normal drawing.

Shared calling and shared devices are not the same thing

People conflate two Microsoft ideas that solve different bills.

Shared Calling (one number, many people)

A resource account holds the phone number. Users get a Teams Phone license and a policy that lets them place outbound PSTN calls through that number. They do not each need a DID or a calling plan.

Use it for staff who rarely call out: warehouse, seasonal help, people whose customers already reach them on a main auto attendant. Do not use it for anyone who must be called back directly, or who lives on inbound sales.

Shared devices / common area (one phone, many hands)

A lobby phone, a shop floor phone, a conference room that must be able to dial 911 and the front desk — those are accounts licensed as Microsoft Teams Shared Device (Shared Space), not as a person. The handset stays on the wall. Nobody signs into their own mailbox on it.

That is the opposite of “give every employee a desk phone.”

Full Teams Phone users

Knowledge workers, reception, and anyone with a published direct number get:

  • A Teams Phone license plus a connectivity method (plan, Operator Connect, or Direct Routing)
  • Their own number (or a clearly documented main-line + extension story)
  • Voicemail in the tenant, call forwarding, delegation / shared line appearance if an assistant answers for them
  • The same identity they already use for Teams chat and meetings — that is the point of putting the PBX here

Reception often needs a queue or auto attendant in front of people, not a personal DID that rings into the void at lunch. Design the attendant first, then the humans.

Do they need a handset?

Default: no. The Teams client on a PC with a decent headset, plus the mobile app, is a complete business phone for most office and hybrid staff. Call history, transfer, hold, and voicemail are the same place they already work. A second device on the desk is another thing to fail, another thing to provision, and another thing that does not travel.

Buy a certified Teams phone when at least one of these is true:

  • Hands and eyes are busy. Warehouse, shop, clinic hallway. Gloves, grease, or a need to grab a handset without unlocking a PC.
  • The desk is shared or has no PC. Common area, gate, waiting room, spare office. This is a shared-device license, not a user phone.
  • The job is answering all day. A dedicated receptionist who lives in a queue often prefers hardware hookswitch, a hardware mute, and a sidecar / busy-lamp look. The client can do the job; the handset is about fatigue and habit, which are real.
  • Hearing, motor, or policy needs a physical control. Some people cannot or will not take calls on a headset-PC combo. Meet them there.
  • You still have analog or paging you have not replaced. Then the phone is part of Direct Routing, not a lifestyle choice.

Do not buy a handset because “we have always had a phone on every desk,” because the vendor’s quote included fifty of them, or because someone is anxious that Teams is not a real phone. It is a real phone. The number is the real asset. The plastic is optional.

A useful rule: if the person already spends the day in Teams on a laptop, give them a headset and a DID (or Shared Calling if they do not need a DID). If the person does not have a laptop at the place the phone must ring, give the place a shared device. If you cannot say which of those two sentences applies, you are not ready to order hardware.

A compact rollout

  1. Map personas: main line, knowledge worker, frontline, common area, analog leftover.
  2. Pick PSTN connectivity per site, not one slogan for the whole company.
  3. Assign personal numbers only to people who will be called on them.
  4. Put Shared Calling on the rest of the licensed users who still need outbound PSTN.
  5. Put shared-device licenses on wall phones and rooms.
  6. Order handsets last, against that list, not against headcount.

Identity still has to be right — MFA, device policy, no shared passwords on a lobby phone’s user account. That sits in Intune and authentication.

If you want this designed against a floor plan and a phone bill instead of a slide, contact EAC Partners.