Ofcom UK Directs Tismi to Block Specific Phone Numbers Due to Serious Misuse

The UK telecoms regulator, Ofcom, has issued an update on their investigation into communications provider, Tismi (Tismi BV), which directs the company to “block all calls and messages” sent to or from specific mobile numbers allocated to it by the regulator after they were “linked to serious fraud or misuse“.

The original investigation, which was launched in October 2024 (here), occurred because Ofcom had cause to deem it necessary to assess whether the company had failed in its duty to ensure that phone numbers allocated to it are not being misused, including to perpetrate scams.

The probe reflected the fact that Ofcom had previously launched an enforcement programme during February 2024 to ensure that UK telephone and text companies were using phone numbers efficiently and effectively. This formed a complementary part of their effort to strengthen existing rules against the use of “fake phone numbers” and “spoofed calls“, which included a measure for phone providers (fixed line and mobile) to introduce stricter controls against “Presentation Numbers” that are used to identify who is making a call (here).

Ofcom allocates telephone numbers, usually in large blocks, to telecoms firms, which can then transfer those numbers to individuals or other businesses as their customers. But the regulator’s investigation raised concerns that some of the numbers they’d previously allocated to Tismi “are/were being misused, including to facilitate scams“. The latest update to this probe reveals that they’ve now issued Tismi with a direction to take action.

Ofcom’s Direction to Tismi

In accordance with section 49 of the Communications Act 2003 and General Condition B4.4 of Ofcom’s General Conditions of Entitlement, Ofcom has issued a direction to Tismi B.V. (Tismi), registered company number KVK-32081827, and part of Link Mobility.

Ofcom has received information that indicates that mobile numbers allocated to Tismi by Ofcom have been linked to serious fraud or misuse.

Based on the information received by Ofcom, we have issued a formal direction to Tismi, requiring Tismi to block all calls and messages sent to or from specific mobile numbers allocated to it by Ofcom. Tismi was sent the direction on 20 June 2025 which requires Tismi to comply with the requirements set in the direction by 24 June 2025.

Annex A11 of Ofcom’s Regulatory Enforcement Guidelines sets out the process that Ofcom will usually follow when it issues a direction under GC B4.4.

The investigation itself still appears to be open and ongoing, so this may reflect action that Ofcom felt needed to be taken urgently and before they’d reached a final conclusion. The regulator has the power to level a significant fine against operators that aren’t following their rules, and may also enforce strict process changes to help prevent any reoccurrence.

Tismi, part of Link Mobility Group from 1st Jan 2021, describes itself as being a national telecom operator active in the UK, Switzerland, Iceland, Netherlands.