Ofcom Probe BT and Three UK Over Outages of Mobile Calling and 999 UPDATE

The UK telecoms and media regulator, Ofcom, has this morning launched fresh investigations into mobile network operators EE (BT) and Three UK following network outages in the summer that resulted in UK-wide disruption to mobile call services, including to emergency services (e.g. 999 for police, fire, ambulance etc.).

The regulator’s existing General Conditions rules (e.g. General Condition A3.2 and sections 105A, 105C and 105K of the Communications Act 2003) require every communications provider to “ensure the fullest possible availability of public communications services at all times, including in the event of a disaster or catastrophic network failure, and uninterrupted access to emergency organisations.”

Suffice to say, any failure of such systems, particularly to the emergency services, is extremely serious due to the risk that it could result in a loss of life. This is particularly relevant now that broadband ISPs are increasingly switching away from traditional landline phone services and on to IP-based digital phone alternatives (inc. VoIP), which may be more exposed to connectivity problems, power cuts and complexities around location reporting etc.

The issue has already been underlined on several previous occasions, after a string of broadband and VoIP providers, including BT, Gigaclear and Vonage, were hit with Ofcom fines over related failings (here, here and here). The disruption BT’s network suffered in 2023 is particularly notable, given today’s news.

Fast-forward to today and BT has now notified Ofcom of a “software issue” that resulted in a UK-wide disruption to mobile call services interconnecting to and from EE’s mobile network on 24th and 25th July 2025. “This resulted in BT and EE customers being unable to make or receive mobile calls to other networks and emergency services,” said Ofcom.

Separately, Three UK has notified Ofcom of an incident that resulted in a UK-wide disruption to call services on 25th June 2025, including customers’ ability to contact emergency services. “Our investigations will seek to establish the facts surrounding these incidents and asses whether there are reasonable grounds to believe that BT and Three have failed to comply with their regulatory obligations,” said Ofcom.

A BT Group spokesperson told ISPreview:

“We are aware that Ofcom has begun an investigation into the technical fault impacting voice calls on our network on 24th and 25th July 2025. We will co-operate fully with Ofcom throughout the investigation and apologise again for any issues caused by this incident.”

Such investigations can take a bit of time to run their course, so we might not learn the final outcome until later in 2026. But past evidence suggests that BT and Three UK may be likely to face a sizeable financial penalty.

The BT (EE) Investigation
https://www.ofcom.org.uk/../investigation-into-bt-following-voice-service-interconnect-outages-on-24-and-25-july-2025

The Three UK Investigation
https://www.ofcom.org.uk/../investigation-into-three-following-voice-service-outage-on-25-june-2025

UPDATE 10:01am

We’ve added a comment from BT above.