EE says it carried out further work overnight to fix a technical problem which left some customers unable to make or receive calls.
In the last 24 hours, hundreds of people who use the mobile provider have told the BBC they have experienced service issues.
It comes after thousands were left unable to make or receive calls earlier this week due to a technical issue which impacted both mobile and landline phones.
On Saturday, a spokesperson for BT – which owns EE – said the network was “running as normal” after maintenance was carried out last night, but that it was “monitoring” the situation.
The BBC’s Your Voice, Your News continued to receive messages from readers on Saturday saying that they had experienced issues with their phone service.
One 84-year-old customer said she and her husband were left unable to make “vital” daily calls to their daughter and son-in-law.
“The service is still down, into our third day of no service is unacceptable,” said another customer from Essex, who added that “the lack of information is deafening”.
“This is still an ongoing issue,” reported another customer from Exeter, who said multiple offices of his estate agency business were all experiencing problems making calls.
Earlier this week, EE customers reported that they were unable to make or receive calls, including to 999.
BT apologised for that outage on Thursday and said that it happened “following a technical fault impacting voice services” on their network.
Responding to the latest outage, EE said on Saturday: “We continue to conduct enhanced monitoring to prevent recurrence.
“We sincerely apologise for any inconvenience this issue has caused.”