Your phone system has run reliably for years. Then the maintenance contract ends, spare parts get scarce, and your service team is missing features a pure PBX never had. There is usually no hard deadline for switching: in Germany, the Federal Network Agency’s January 2026 concept for the copper-to-fibre migration names no shutdown date and instead proposes around three years’ notice from the shutdown announcement. That works in your favour, because you can plan the move calmly.
Why a cloud-based platform can pay off is covered elsewhere. This article is about the project itself: how phone numbers, parallel running and training fit together so that your customers notice as little as possible.
Inventory: what is really connected to the old system
Systems that have grown over the years contain more than the documentation says. Before you configure anything new, list the following:
- Phone numbers: all main numbers, direct-dial ranges and rarely used numbers that still appear on old flyers or invoices.
- Call flows: announcements, groups, forwarding, rules for after hours and public holidays. Ideally, call in yourself and note what actually happens.
- Attached devices: fax, door intercom, DECT handsets, lift emergency phone, alarm system. Safety-related devices in particular need their own solution and often a longer lead time.
- Interfaces: dialling from the CRM, customer data pop-ups, exports for controlling.
- Workstations: not everyone has to move. Computerwoche describes grouping users by need; special cases such as control rooms or production areas may stay on a small on-site system.
Phone numbers: the most delicate part of the project
In Germany, you can take your established numbers with you. Section 59 of the Telecommunications Act (TKG) grants this right and limits any interruption during a provider switch to one working day at most. Geographic numbers are tied to their location, however, so if you are moving to another local network at the same time, clarify this early. Rules differ in other countries. In practice, four points matter:
- Do not cancel prematurely yourself. The new provider leads the switch and coordinates it with the old one. After a contract ends, there is only about a month left to request number porting, and you should not rely on that.
- Match master data exactly. Company name, address and contract holder must match the details held by your current provider. Discrepancies are a common reason for rejection, and each one costs days.
- Think in whole ranges. Direct-dial ranges are normally transferred complete. If you only want to keep part of one, clarify that before placing the order.
- Choose the date deliberately. Not a Friday, not the day before a long weekend, and not during your own peak season. If something goes wrong, someone who can fix it needs to be available the next day.
Check your network and connection in advance
Voice will now run over your data network. According to Computerwoche, only part of an office workforce is on the phone at any one time, typically 10 to 30 percent. In a contact centre it can be 100 percent. So calculate for your actual peak load and review the firewall and voice prioritisation together with your internal network.
Your connection also needs scrutiny: is the guaranteed availability sufficient, how quickly are faults repaired, and who is responsible when something fails? Decide, too, where calls go if the line at your site goes down. Our article on resilient service communication goes into more detail. Also clarify how emergency calls are routed at each site.
Parallel running instead of a big-bang switch
It gets risky when everyone changes over on the same Monday morning. A staged approach has proven its worth:
- Pilot: a small team works in the new system via a test number, starting with the basic functions.
- Rebuild the flows: phone menu, groups and service hours. This is also a good moment to leave old baggage behind.
- Scripted test calls: from outside, outside service hours, against holiday rules, with a busy group, with forwarding and with consultation calls.
- Move teams one after another: the old system stays reachable until the main numbers have been ported.
- Define a way back and set an end date: what happens if the cut-over fails? And when will the old system be switched off for good? Without a date, its costs simply keep running.
The team and the first weeks of operation
Train shortly before the switch and around real situations: answering, transferring, holding a consultation call, setting a break, creating a callback. A list of features rarely sticks. Each team should have one person with deeper training as the first point of contact.
Plan slightly higher staffing for the first days after cut-over and a short route for reporting faults. For two weeks, check reachability, abandoned calls and transfers daily and compare them with the old system’s figures where available. And do not take on everything at once: once telephony is stable, further channels such as chat, email or WhatsApp can follow in separate steps.
myContactCenter from ilogixx brings telephony, chat, email, WhatsApp and ticketing together in one interface. This lets you build call flows and reports in one place during parallel running and add channels gradually later on.
Conclusion: numbers and processes first, technology second
Moving from a phone system to a contact centre is less a technology project than a question of sequence: record what you have, prepare your numbers carefully, check the network, switch in stages and support the team. Plan it that way and you will not have to explain a day of downtime to your customers.
Planning to replace your phone system? Book a consultation via the online calendar at ilogixx.de. We will go through your current setup together and work out which steps make sense in your case.
