How to Keep Your Existing Luxembourg Numbers When Moving to Teams Phone

How to Keep Your Existing Luxembourg Numbers When Moving to Teams Phone

by PBX.lu Editorial on October 12, 2026

How to Keep Your Existing Luxembourg Numbers When Moving to Teams Phone

Your phone numbers are on your invoices, your website, your vans and in your customers' contacts. Moving your calls to Microsoft Teams should not mean changing them. In Luxembourg, you can almost always keep every number. What changes is who moves them, how long it takes and how much control you keep afterwards.
This guide explains the three ways to bring your numbers into Teams, why Direct Routing suits number porting so well, which Luxembourg operators offer it, and a step-by-step plan for the switch. For the wider choice of Teams calling path, see our guide to Microsoft Teams calling in Luxembourg.
🧭 On this page: The short answer · Three routes for your numbers · Why Direct Routing suits porting · Operators in Luxembourg · Step by step · Numbers that need extra care · Common questions

The short answer

📌 You can keep your Luxembourg numbers with all three Teams calling paths. With Microsoft Calling Plans, Microsoft takes over the numbers. With Operator Connect or Direct Routing, a local operator ports them under the rules of the ILR, the Luxembourg regulator. Direct Routing also lets you keep numbers Microsoft cannot take, move staff in stages, and leave Teams later without porting again.
Number porting Moving an existing phone number from one operator to another. The number stays the same; only the company behind it changes.

Three routes for your numbers

Every Teams calling path needs your numbers to live somewhere. Where they live decides who runs the port and which rules apply.
☁️ Microsoft Calling Plans: numbers move to Microsoft. You submit a port order in the Teams admin centre, with a signed Letter of Authorisation and a recent invoice from your current operator. For Luxembourg, Microsoft states a lead time of 5 to 30 business days. Only geographic numbers can be ported. Toll-free numbers cannot.
🔌 Operator Connect: numbers move to a certified operator. The operator ports your numbers under ILR rules, then makes them available in your Teams admin centre. You assign them to users there.
🛡️ Direct Routing: numbers move to an operator you choose. The operator ports your numbers to its network and connects them to Teams through a Session Border Controller. If your current operator offers Direct Routing, there may be nothing to port at all.
Session Border Controller (SBC) A secure gateway that links Teams to an operator's phone network. It can sit in your office or a data centre, or be run by the operator as a service, which is the usual choice for smaller companies.
Letter of Authorisation (LOA) A signed form that allows the new provider to request your numbers from your current operator.
🕒 Porting into Microsoft in Luxembourg: the fine print
Microsoft runs Luxembourg ports on weekdays in two time slots, 08:00 to 11:00 and 13:00 to 16:00 Central European Time. Changes or cancellations must reach Microsoft two business days before the porting date. Ported numbers arrive unassigned, so you assign each one to a user afterwards. Partial ports, where only some numbers on an account move, depend on your current operator.

Why Direct Routing suits number porting

Operator Connect and Direct Routing both keep porting with a local operator. Direct Routing goes one step further. Your numbers stay on the network of an operator you choose, and Teams becomes one of the places they can ring. If you want the technical background first, read how Direct Routing works in Microsoft Teams.
1. The port follows Luxembourg rules. A Luxembourg operator runs the port under ILR rules. Porting is free for you, activation must happen within one working day of the agreed date, and your old operator must keep your service running if the transfer fails. In practice, allow about five working days from order to switch.
2. Sometimes there is nothing to port. If your current operator already offers Direct Routing, your numbers stay where they are. The operator connects them to your Teams account. There is no port order, no porting date and no risk window.
3. More number types can come along. Microsoft's Luxembourg porting covers geographic numbers only. Through Direct Routing, an operator can bring in what it holds for you: direct-dial ranges, 800 freephone numbers and numbers in other countries. The SBC also converts Luxembourg numbers, which often add extension digits to a short base number, into the full international format Teams expects.
4. You can move in stages. Your numbers stay on the operator's network and are pointed at Teams one by one. Sales can move this month and reception next quarter. Your main number can stay on a Cloud PBX for queues and opening hours while staff call from Teams. This mixed setup is often called hybrid.
5. Your numbers are not tied to Teams. If you change platform later, the operator re-routes your numbers instead of porting them again. If Teams or your internet connection goes down, the operator can send calls to mobiles or another number. Microsoft explains the setup in its Direct Routing planning guide.
🔑 Key point. With Direct Routing, your numbers depend on your contract with a local operator, not on your Teams licence. That is what keeps your options open.
⚠️ The trade-off. Direct Routing adds an SBC and one more company to coordinate. If a local operator on Operator Connect meets all your needs, that model is simpler to run. Our Direct Routing guide for IT managers covers who owns what.

Luxembourg operators offering Direct Routing with number porting

These operators publicly offer Microsoft Teams Direct Routing with Luxembourg numbers. Confirm porting terms, lead times and SBC hosting directly with each one.
📡 Mixvoip LU
Direct Routing through certified SBCs, with number portability in more than 25 countries. Registered with the regulators in Luxembourg, Belgium and France, with a German entity in Trier. Also runs a Cloud PBX, so Teams and a phone system can share the same numbers.
🔗 Cegecom LU
Offers both Direct Routing and Operator Connect for Teams. Presents its Direct Routing offer as a way to keep your existing Luxembourg numbers.
🔵 DEEP LU
The business brand of POST Luxembourg. Its MS Teams CloudVoice offer is built on Direct Routing and lists keeping your Luxembourg numbers as a benefit. If your numbers are already with POST, ask whether a port is needed at all.
🟣 Proximus NXT LU
Offers Teams Direct Routing in Luxembourg, drawing on its work as both integrator and operator. Its public material does not describe the porting process, so ask about it directly.

Step by step: keep your numbers during the move

  1. List every number. Main number, direct lines, fax, alarm and lift lines, freephone numbers and numbers abroad. Note what each one does today.
  2. Check your current contract. Porting is free, but leaving a fixed-term contract early can still cost you. Note the end date.
  3. Choose the calling path and operator. Decide where your numbers will live: with Microsoft, an Operator Connect operator or a Direct Routing operator.
  4. Prepare the porting details. The exact legal name on your current account, your customer number, a recent invoice and the full number list. Details that do not match are the most common reason a port is rejected.
  5. Set up Teams before the porting date. Licences, users, call routing and an emergency address for each location, so 112 calls carry the right address. Test with temporary numbers.
  6. Agree the date and keep the old line active. Do not cancel your old contract yourself. The port ends it.
  7. Test right after the switch. Call every key number from outside, check the caller ID on outgoing calls, and confirm with your operator that emergency addresses are delivered correctly.
The full ILR process, documents and cross-border rules are in our business number porting guide for Luxembourg.

Numbers that need extra care

Direct inward dialling (DID) A number that rings one person or team directly, without going through reception.
  • Direct-dial ranges. Many Luxembourg numbers add extension digits to a base number. Check that every line can be shown as a full number in Teams.
  • Freephone 800 numbers. Microsoft cannot port Luxembourg toll-free numbers into Calling Plans. Keep them with an operator and route them through Direct Routing or your Cloud PBX.
  • Fax, alarm and lift lines. Teams does not handle these. Keep them on a separate line or an analogue adapter from your operator.
  • Mobile numbers. These stay with your mobile operator. Some operators offer fixed-mobile convergence, which links mobile numbers to your business phone system.
  • Numbers in Belgium, France or Germany. Each country has its own porting rules. An operator registered in each country keeps this simpler.

Common questions

❓ How long does it take to keep my numbers when moving to Teams?
With a Luxembourg operator, allow about five working days for a clean port, with at most one working day of downtime. Microsoft states 5 to 30 business days for ports into Calling Plans. Large number ranges take longer.
❓ Can I keep my numbers and my Cloud PBX?
Yes. With Direct Routing, Teams can connect to a Cloud PBX. Your numbers stay on the PBX, which keeps queues and reception, while staff call from Teams. See the Microsoft Teams integration feature.
❓ What happens if the port fails?
Under ILR rules, your old operator must keep your service running until the new operator activates the numbers. Agree a fallback plan anyway: who you call, and where calls go if something breaks on the day.
📚 Planning the rest of your Teams move? Explore the features guide or compare providers active in Luxembourg and the Greater Region. Terms explained in the glossary.
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