The complete UK guide to safely identifying an unknown caller — free reverse-lookup tools, premium-rate prefixes never to call back, carrier call-blockers, and the verification rules for any unknown number.
Last reviewed: 22 May 2026 · ScamSupport research
An unknown number has called or messaged you, and you want to know who it is before responding. One thing to know first: there is no official UK service that names the private individual behind a number — data-protection law prevents a public register of mobile owners. What you can do, free and in under a minute, is identify what kind of number it is and whether other people have reported it as a scam. That is almost always all you need.
Start here: what to do BEFORE calling back any unknown UK number
The single most important rule: don’t call back an unknown number until you’ve looked it up. An unknown UK number can be a genuine call (delivery driver, recruiter, GP), a Wangiri / premium-rate trap, or a spoofed scam ID. A 30-second lookup tells you which one you’re dealing with. The flow:
Check the prefix first. If it starts 070 / 084 / 087 / 09 / 118, a callback can incur premium charges — full prefix list below.
Look it up on a crowdsourced UK number database. who-called.co.uk and UK Trust Score both maintain free public records of UK number reports.
If clean: call back if you want; voicemail if not. Real callers leave a message.
If reported as scam: block the number and report via 7726 (SMS) / Report Fraud (financial loss).
who-called.co.uk — the largest UK-specific crowdsourced number database. Reports include scam type categorisation (PPI, courier, bank fraud, Wangiri). Free, no sign-up needed.
UK Trust Score — UK-focused with risk scoring and recent-activity timestamps. Good for cross-checking who-called results.
Should I Answer? — UK reverse-lookup database with phone-app companion (iOS / Android) for real-time call screening.
NumberDB — international coverage including UK; useful for cross-border numbers.
App-based callers ID services (real-time during call)
Truecaller (iOS / Android, free tier) — world’s largest caller-ID community database with real-time identification when a call comes in. Free version has limitations; premium £3-5/month removes them.
Hiya (iOS / Android, free) — carrier-grade caller-ID service. Default on Samsung devices in some regions. Identifies known scam patterns automatically.
RoboKiller (paid) — subscription service that pre-screens calls against a known-scammer database and lets the call through only if cleared.
Telephone Preference Service (TPS) — the UK’s official no-unsolicited-marketing-calls register. Free. Registering your number doesn’t block scams (which already ignore TPS) but stops legitimate marketing calls.
Ofcom doesn’t provide a public lookup but accepts complaints about specific numbers at ofcom.org.uk/phones/scam-calls-and-messages. Complaints feed into network-level blocking decisions.
UK premium-rate & high-charge prefixes — never call back without checking
A callback to any of these prefixes can incur charges above standard call costs. Some are several pounds per minute.
Prefix
What it is
Typical cost
070, 0700–0709
Personal numbering (forwarded to another destination)
Up to £3.40/min
084, 0843, 0844, 0845
Business-rate numbers
7-13p/min + access charge
087, 0870–0873
Higher business rate
Up to 13p/min + access charge
09, 0900–0909
Premium-rate
60p–£3.60/min + service charge
118
Directory enquiries
£3+ per call + per-minute
Free UK prefixes: 0800 / 0808 (freephone), 0300 / 0345 (national-rate from any UK phone, charged at standard rate, no premium). Real UK government services, NHS, and most large businesses use these.
How to identify common UK number categories
UK area-code lookups (geographic landlines)
UK landlines start 01 or 02 followed by area code. Examples: 020 = London, 0121 = Birmingham, 0131 = Edinburgh, 0141 = Glasgow, 0151 = Liverpool, 0161 = Manchester, 0114 = Sheffield, 0117 = Bristol. Full list at area-codes.org.uk. An area code that matches your physical location doesn’t mean the call is local — caller ID is trivially spoofed (see our spoofed phone number guide).
UK mobile prefixes
UK mobiles start with 07 followed by 9 more digits. Specific prefixes (07700, 07911 etc.) don’t reliably indicate network — mobile number portability means a customer can move between networks while keeping their number. Don’t use prefix as evidence of legitimacy.
International prefixes you might see
The most-frequently-flagged international scam-call prefixes targeting UK consumers in 2026: +231 (Liberia), +252 (Somalia), +373 (Moldova), +675 (Papua New Guinea), +509 (Haiti), +1-664 (Montserrat), +1-787 (Puerto Rico). If you receive a missed call from a country code you don’t recognise, treat it as Wangiri-suspect. (See our one-ring call scam guide.)
Sky Mobile — standard scam-call filtering enabled by default; per-customer blocklist via Sky Mobile app.
BT Call Protect (landline) — free for BT landline customers. Blocks international, withheld and known-scam numbers.
Virgin Media Phone block — per-line block list for landline.
Phone-app native call-silencing (works on every modern phone)
iOS: Settings > Phone > Silence Unknown Callers. Unknown numbers (not in your contacts, not in recent outgoing calls) go straight to voicemail. Known contacts still ring.
Android (stock): Phone app > three-dot menu > Settings > Caller ID & Spam > enable “Filter spam calls”. Variants exist on Samsung One UI, Pixel UI, etc.
Both: add suspected scam numbers individually to your block list via Recents > tap (i) / long-press > Block.
If you’ve received an unknown call: the 4-step verification flow
Don’t answer; let it go to voicemail. Real callers leave a message. Scammers usually don’t.
If you answered and the caller asks for personal details / money / OTP codes: hang up. The verification rules from our smishing pattern guide apply identically to phone calls: never share OTPs, never call back numbers given in the call, never transfer money for “your safety”.
Look up the number on who-called.co.uk and UK Trust Score. Cross-check both. If multiple recent scam reports, you have your answer.
Block + report. Block the number on your phone, report scam SMS to 7726, report financial loss to Report Fraud at 0300 123 2040.
If you’ve already lost money or shared data after an unknown-number call
Financial loss to a UK bank transfer: Use the PSR Claim Wizard — PSR Mandatory Reimbursement covers up to £85,000 within 5 working days for APP fraud.
Crypto / gift cards / wire transfer: Report to Report Fraud; recovery is limited.
Personal data shared (DOB, NI number, address): consider CIFAS Protective Registration — 2 years of credit-file protection.
Premium-rate call charges: contact your carrier for a goodwill refund; escalate to Phone-paid Services Authority if refused.
Frequently asked questions
How do I find out who is calling me from a UK number?
There is no official UK service that names the private individual behind a number, but you can identify the caller's nature: check the prefix, then look the number up on a crowdsourced UK database such as who-called.co.uk or UK Trust Score, where other people report scam and nuisance calls.
Can I look up who owns a phone number for free in the UK?
For businesses and published landlines, often yes — a web search or an online directory will name them. For mobiles and withheld or spoofed numbers there is no free public owner-lookup; UK data-protection rules prevent a public register of private mobile owners. The practical free option is a crowdsourced call-reports database.
Should I call back an unknown number?
Not until you have checked the prefix. A callback to an 070, 084, 087, 09 or 118 number can cost several pounds a minute. If the prefix is a normal one and the number is not reported as a scam, calling back is fine — but a genuine caller will usually have left a voicemail.
How can I tell if a number is a scam?
Look it up on who-called.co.uk and UK Trust Score — multiple recent scam reports are a strong signal. Treat as suspicious: missed calls from unfamiliar international codes (the Wangiri trap), 070 personal numbers, and any caller who pressures you for personal details, security codes or money.
Why does a scam call show a UK number, or even my own area code?
Caller ID is easily faked — this is called spoofing. Scammers display a local-looking or trusted number to make you answer. The number you see is not proof of who is calling; see our spoofed phone number guide.
What should I do if I have already been scammed by a phone call?
If you transferred money from a UK bank, contact the bank immediately and use the PSR reimbursement route. For card payments use chargeback or Section 75. If you shared personal data, consider a CIFAS protective registration. Report it to Report Fraud on 0300 123 2040.