- Prefix
01603 5- Area
- Norwich
- Number type
- Geographic landline (01/02)
- Format
01603 5XXXXX- From abroad
+44 1603 5XXXXX- Ofcom blocks in range
- 73
- Blocks in service
- 60
- Range holders
- 27
What are 01603 5XXXXX numbers?
Any UK number matching 01603 5XXXXX sits in the
01603 dialling code for Norwich.
Ofcom hands these numbers to communications providers in blocks; this range
contains 73 blocks, of which
60 are allocated and usable. Calls from these
numbers are typically homes and businesses in the Norwich area — or
organisations elsewhere that keep a local 01603 presence using
VoIP.
Who holds 01603 5… number ranges?
| Range holder (allocated by Ofcom) | Number blocks | Example range |
|---|---|---|
| Vodafone Ltd (C&W) | 8 | 01603 540XXX |
| Gamma Telecom Holdings Limited | 7 | 01603 51XXXX |
| BT | 6 | 01603 50XXXX |
| Sky UK Limited | 6 | 01603 526XXX |
| Colt Technology Services | 4 | 01603 561XXX |
| TGL Services (UK) Ltd | 4 | 01603 530XXX |
| Redcentric Solutions Limited | 3 | 01603 580XXX |
| Lumen Technologies UK Limited | 2 | 01603 550XXX |
| TalkTalk Communications Limited | 2 | 01603 568XXX |
| Ccpro Solutions Limited | 1 | 01603 522XXX |
| Citrus Telecommunications Ltd | 1 | 01603 525XXX |
| Core Telecom Limited | 1 | 01603 523XXX |
…and 15 more providers hold smaller allocations in this range.
Ofcom’s data shows the provider each number range was originally allocated to — not who holds an individual number today. Numbers are frequently moved (ported) between providers, and no public database reveals the person or business behind a specific number, so treat any service that claims to with suspicion.
Not every block in this range is in service: of the 73 blocks Ofcom lists, 13 are protected (reserved by Ofcom and not in use). A call appearing to come from an unallocated block is a strong sign of a spoofed number.
Is a call from a 01603 5… number safe?
A local-looking number is never proof of who is calling: fraudsters spoof 01603 caller IDs so their calls look like they come from Norwich (‘neighbour spoofing’). If an unexpected caller asks for personal, banking or one-time-code details, hang up and ring the organisation back on a number you find independently. To put a name to a caller, see who called me?; to report one, see how to report a scam number.
Check a specific 01603 5XXXXX number
Paste any full number into the checker above (or on the main phone number checker) to see its exact range holder and allocation status from this week’s Ofcom data.
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