People using Three’s mobile network found themselves unable to receive calls from customers using EE phones.
Users could make outgoing calls, send texts and use data, but some experienced “connectivity issues”.
A Three spokesperson said: ““Some of our customers did experience connectivity issues earlier today. A problem at EE’s end meant Three customers could not receive voice or SMS services from EE customers. We worked with EE to resolve the issue quickly
“This problem has now been resolved and all services have been restored. We are sorry for any inconvenience caused.”
Earlier this year the Three network overhauled its provision for allowing customers to with certain handsets.
In May it trialled for everyone using its network in the UK. It said the scheme would save users’ data allowance and boost privacy.
* This article has been updated to make clear that the problem related to Three customers being unable to receive calls only from EE customers. 13/6/17