A multi-department organisation needed to move approximately 500 DDI numbers from a legacy carrier arrangement to a modern SIP-based platform. The number range included main lines, direct numbers, fax replacements, alarm references and rarely used services.
The requirement
The challenge was data quality. Old invoices, PBX records and departmental spreadsheets did not fully agree. A single bulk port without validation could have moved inactive numbers, omitted important services or created routing failures.
The proposed telecoms design
The migration plan created a master number register showing current provider, installation address, destination, owner, criticality and target route. SIP capacity, emergency calling information, fraud controls and inbound failover were considered alongside the port.
Delivery approach
- Collect carrier invoices and complete number records.
- Validate range ownership and installation addresses.
- Identify critical and low-risk pilot numbers.
- Test the SIP platform and route pilot services.
- Move remaining ranges in controlled batches with agreed rollback actions.
Commercial and operational outcome
The staged approach reduced uncertainty and created a reliable number inventory for future administration. Departments knew which numbers they owned and where calls should route. The organisation also avoided treating a complex number estate as a single administrative form.
What this scenario demonstrates
Number porting is a controlled operational change. Accurate records, realistic lead times, emergency information and test plans are essential. No port date should be treated as final until the losing and gaining providers have accepted the order.
Next step
Use UKDDI to search for new UK business numbers, or ask 39T to plan SIP trunking and number porting for an existing estate.