A technical problem with EE appears to have left its customers unable to receive calls and texts.

The problems mean that Vodafone customers and those on other networks cannot call phone numbers registered with EE. But it also means people can’t call those who have ported their phone number to other networks from EE in the past – even if they are no longer on the network.

Vodafone had received particular complaints on Down Detector and other tracking websites, and EE suggested that the problems particularly affected calls originating from that network. But Vodafone said its network was not experiencing any problems and that the problem occurred within EE’s infrastructure.

“We can confirm that there were no issues with the Vodafone network today; However, some of our customers have been affected by an issue with the EE network – which we believe should be resolved as soon as possible,” Vodafone said. “This meant some customers were unable to connect calls to EE numbers, and the issue also affected customers who had already transferred their number from EE to Vodafone.”

EE said the problem specifically related to Vodafone numbers. He said calls from other networks should work.

“We are aware that some of our mobile customers are unable to make or receive calls from a Vodafone number,” EE said in a statement. “We are working quickly to resolve this issue and are truly sorry for any inconvenience caused. Calls to other networks, mobile data and text messages are not affected.

It’s unclear to what extent the issue only affected Vodafone users. Some Virgin Mobile, O2 and Three customers have reported having problems making calls.

Phones did not need to always be with EE to have difficulty receiving calls, due to the way ported numbers work on the UK telephone infrastructure. Even when a phone number is moved to another network, it initially retains the prefix that identifies it as part of the old one – and therefore all calls made to that number are briefly routed through the infrastructure from the legacy network, meaning customers may face issues with providers they left long ago.

The problems began early Monday afternoon in the United Kingdom, when customers said they were experiencing a series of unusual problems. Some Vodafone customers said they could call other people on the same network, but not talk to people using other providers, for example.

However, on different networks, data and Internet connections seemed to work normally.

On Twitter, Vodafone first responded to affected users, apologizing and asking for more information. He encouraged affected users to check its online service checker – which indicates that there are problems in certain areas.

Some subsequent tweets sent by Vodafone suggested the problem could be caused by an “EE network issue affecting calls and text messages.” But Vodafone users have also reported struggling to call other networks, such as Three.

On tracking site Down Detector, problems have been widespread across the UK, with some areas like London, Manchester and Edinburgh particularly affected, according to the same website. But that may simply be due to where customers tend to be based.

Vodafone has 18 million customers in the UK for its mobile and landline offers. It is the UK’s third largest mobile operator, after O2 and EE.

It is currently in the process of merging with another relatively small UK mobile network, Three. The companies said “greater coverage and reliability” would be one of the benefits of the deal, which is expected to take place in 2024 if it goes through.

When this deal was announced, analysts noted that both companies were “lagging behind in Internet performance between broadband and mobile services.”

The last numbers come after Vodafone suffered a major outage in April which left its home broadband customers without a connection.. It said this outage only affected one percent of its customers.