What has Ofcom fined Tismi for?
Ofcom has fined the telecoms provider Tismi £437,500 for failing to take appropriate and proportionate steps to stop phone number misuse. That includes numbers being used to carry out scams. Ofcom announced the fine on 21 October 2026, on its own news page.
Ofcom says the money will be passed to HM Treasury. It also says the penalty includes a 30% discount on what it would otherwise have been, because Tismi admitted liability.
Tismi supplies phone numbers to its customers, rather than selling you a mobile plan. That is why the case matters for phone number misuse: scammers need working numbers, and those numbers have to come from somewhere.
Key takeaways on phone number misuse
- Ofcom fined Tismi £437,500 on 21 October 2026 over phone number misuse.
- Ofcom says Tismi had no appropriate or proportionate measures in place between at least November 2022 and January 2025.
- Ofcom has also opened a new investigation into Xtra Phones UK. That is not a finding against the company.
- Nothing here changes what you should do about scam calls and texts: report them, and do not click links.
How does phone number misuse happen?
Ofcom allocates telephone numbers, usually in large blocks, to telecoms providers. Those providers can then transfer the numbers to individuals or other businesses. Ofcom’s numbering rules say providers must take appropriate steps to make sure numbers it has allocated to them are not misused by the people they transfer them to.
Ofcom says misuse could include using numbers to make scam calls and send scam texts. It expects providers to carry out “know your customer” checks on business customers, so scammers cannot get valid numbers in the first place. It also expects them to keep the risk under review, monitor for misuse and respond to reports of it.
In plain terms, stopping phone number misuse is about the front door. If a provider hands numbers to anyone who asks, without checks, scam callers get the same working numbers as everyone else.
What did Ofcom find about phone number misuse at Tismi?
Ofcom says Tismi did not have any appropriate or proportionate measures in place to prevent number misuse, at least between November 2022 and January 2025. It says the company exposed approximately 366,000 sub allocated numbers to potential misuse for over two years.
Ofcom lists three specific failings. Tismi sub allocated numbers to its customers without carrying out appropriate due diligence. It failed to monitor whether numbers it had passed on were being misused. It also did not have a formal documented process for handling reports of misuse.
During the investigation, Ofcom says it issued a direction to Tismi in June 2025 to block certain numbers so scammers could not keep using them. Tismi put the block in place. Ofcom is also requiring Tismi to complete further actions to show it is complying, including details of its due diligence, its ongoing monitoring and how it responds to reports.
Ofcom’s Director of Enforcement, George Lusty, said: “There’s no excuse for communications providers failing to put in the proper checks and balances to prevent numbers being misused. Today we’re sending a clear message to industry that any company that puts customers at the mercy of scammers will face the consequences.”
What happens next after this phone number misuse fine?
Ofcom has opened a new investigation into Xtra Phones UK, relating to concerns that telephone numbers held by that company are being misused. An investigation is not a finding. Ofcom has not said Xtra Phones UK broke any rule, and we are not saying so either.
Ofcom says this sits under its enforcement programme on phone and text scams, which aims to support good practice in the use of phone numbers and make sure providers follow its rules. Ofcom also says a non confidential version of the Tismi decision will be published at a later date.
This follows the investigations Ofcom opened in September into two other number suppliers, which we covered in our post on what Ofcom’s number misuse probe means for you. As far as we have seen, Ofcom has not announced findings in those cases. The Tismi decision is a separate case.
What can you do about scam calls and texts?
A fine over phone number misuse will not switch off scam calls overnight, so the practical steps still matter. Ofcom’s new Consumer Hub, called On your side, offers tips on protecting yourself against scams, plus advice on common service problems and how to complain. You can find it at ofcom.org.uk/onyourside.
Our guide to scam text messages and the new rules covers the text side, and our post on missed call and job offer scams covers a scam Ofcom warned about earlier this month.
Doing nothing about phone number misuse reaching your own handset is the Do Nothing Default, and it costs you time and patience. Five minutes in your phone’s settings, plus checking what your network offers, is a better habit than waiting for the next ring.
If your contract has drifted past its end date, it is also a fair moment to see what else is out there. Switching will not make scam calls stop, but it can be a good time to check you are not overpaying.
Frequently asked questions about phone number misuse
- What is phone number misuse?
- Ofcom says it is when phone numbers are used in ways that break its numbering rules, which could include using them to carry out scam calls and texts.
- How much was Tismi fined?
- Ofcom fined Tismi £437,500 on 21 October 2026. Ofcom says the penalty includes a 30% discount because Tismi admitted liability.
- Is Tismi a mobile network I might be a customer of?
- Ofcom describes Tismi as a telecoms provider that sub allocates phone numbers to its customers. Check with your own provider if you are unsure who supplies your number.
- Has Ofcom found that Xtra Phones UK did anything wrong?
- No. Ofcom has opened an investigation into concerns that numbers held by Xtra Phones UK are being misused. It has not announced any findings.
- Where can I get Ofcom advice on avoiding scams?
- Ofcom says its Consumer Hub, On your side, offers tips on protecting yourself against scams. It is at ofcom.org.uk/onyourside.
