The Hidden Cost of Technology Upgrades: Legacy Telecom Services Still Billing

When infrastructure changes, old services rarely get cancelled. They just keep billing.

Enterprise technology upgrades are planned carefully. The new infrastructure gets scoped, budgeted, procured and implemented. The project gets signed off. The team moves on.

What doesn’t always happen: the old services get cancelled.

Legacy telecom services continuing to bill after a technology migration is one of the most common and most avoidable sources of enterprise overspend. It happens across data circuits, ISDN lines, network services, legacy voice platforms and mobile services. And because the invoices look similar to last month, they get approved without scrutiny.

The result is money leaving the business every month for infrastructure that is no longer in use.

Why It Happens

Technology migrations are complex. When a business moves from MPLS to SD-WAN, upgrades its voice environment to SIP or UCaaS, or replaces legacy data circuits with new connectivity, the focus is entirely on the new environment. Getting it live, tested and stable is the priority.

Cancelling old services requires a separate process: identifying every service to be decommissioned, submitting formal cancellation requests to carriers, following up on confirmation and reconciling the billing to ensure charges stop. In large, multi-site environments with multiple carriers, this is a significant administrative task.

It is also nobody’s core job.

The project team has moved on. The finance team is approving invoices it can’t easily interrogate. The IT team is managing the new environment. The legacy services keep billing.

Telecom spend wasn’t necessarily incorrect. It was invisible. And invisible cost compounds quickly in complex environments.

The Scale of the Problem

Across enterprise environments in Australia, we consistently find legacy services continuing to bill six, twelve and sometimes eighteen months after the infrastructure they supported was decommissioned.

Common examples include:

• ISDN and PSTN lines still billing after a migration to SIP trunking

• Legacy data circuits still active after an SD-WAN or NBN migration

• Frame relay or MPLS services with no active traffic still generating monthly charges

• Mobile services assigned to staff who have left the organisation

• Collaboration platform licences duplicated across old and new environments

In each case, the services appear on the invoice. The invoice looks similar to the previous month. It gets approved.

The billing doesn’t flag itself as legacy. That identification requires someone with visibility across the full environment — old and new — to map what is still active against what should still be active.

What It Costs

The commercial impact depends on the scale of the environment and how long the services have been running undetected. In our experience, organisations that have been through a significant infrastructure change in the last two to three years without a structured service review are carrying between 10 and 20 percent of their telecom spend in legacy or redundant services.

For an organisation spending $500,000 per year on telecommunications, that is $50,000 to $100,000 in annual spend with no operational value.

There is also a retrospective recovery element. Where legacy services have been billed in error, carriers continuing to charge for services that were contracted to cease, those charges can often be recovered as billing credits. This requires documentation and a formal dispute process, but the credits are recoverable.

We recently completed a review for a large national NFP that had been through significant infrastructure changes. The review identified legacy data network services and voice circuits still billing post-migration. Total outcome: $945,000 in annual spend reduction and $167,000 in billing credits recovered. $1.11M total commercial impact. No new infrastructure required.

The Fix: Visibility Before Anything Else

Recovering legacy cost does not require a new provider, a technology project or significant internal resource. It requires a structured inventory review.

Every active telecom service — across all sites, all carriers, all service types — needs to be mapped against current operational requirements. Each service is assessed against four questions:

• Is this service still in use?

• If yes, is it correctly sized and priced for current usage?

• If no, was a cancellation request submitted and confirmed?

• If cancelled, did the billing actually stop?

This process surfaces the legacy services. Once identified, cancellation requests are submitted, billing is reconciled and where appropriate, credits are claimed for any period where charges continued beyond the agreed cessation date.

In environments with multiple carriers and complex billing, this process benefits significantly from independent eyes. Internal teams are often too close to the new environment to have visibility over what was left behind in the old one.

The Right Time to Do This

Ideally, a structured service review happens as part of every technology migration, a formal decommissioning process that runs in parallel with the new environment go-live.

In practice, that rarely happens. The more common scenario is that the issue surfaces twelve to eighteen months later, when someone asks why the telecom spend is higher than expected given the new, supposedly more efficient environment.

If your organisation has been through any of the following in the last three years, a structured review is worth doing:

• Migration from MPLS or Frame Relay to SD-WAN

• ISDN or PSTN to SIP trunking or UCaaS

• Legacy data circuits replaced with NBN, fibre or cloud connectivity

• Office consolidations, relocations or site closures

• Carrier changes or contract consolidations

Any of these create the conditions for legacy services to continue billing undetected.

Key Takeaways

• Legacy telecom services continuing to bill after a technology migration are one of the most common sources of enterprise overspend

• The services don’t flag themselves, they look like normal charges on a normal invoice

• The fix requires a structured inventory review, not a technology project

• Billing credits are often recoverable for the period where charges continued after services should have ceased

• The right time to review is immediately after a migration — the second best time is now

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If your organisation has been through infrastructure changes in the last few years and hasn’t independently reviewed what’s still billing, it’s worth a conversation.

CDK Telecommunications provides independent telecom audits and billing reviews for enterprise organisations across Australia. No vendor relationships. No commissions. Just commercial clarity.

📩 info@cdktel.com.au  —  1300 235 835  —  cdktel.com.au

CDK Telecommunications  —  Independent  |  Carrier-Agnostic  |  Enterprise-Focused