Wisconsin wireless provider Cellcom has confirmed that a cyberattack is responsible for the widespread service outage and disruptions that began on the evening of May 14, 2025.
The incident disrupted voice and SMS services for customers across Wisconsin and Upper Michigan, leaving subscribers unable to make phone calls or send text messages.
Today, after days of just calling it a technical outage, Cellcom CEO Brighid Riordan has confirmed what was already suspected: that the company suffered a cyberattack.
“We experienced a cyber incident. While this is unfortunate, it’s not something we were unprepared for,” reads a letter from Cellcom CEO Brighid Riordan.
“We have protocols and plans in place for exactly this kind of situation. From the start, we’ve followed those plans — including engaging outside cybersecurity experts, notifying the FBI and Wisconsin officials, and working around the clock to bring systems safely back online.”
“The incident was concentrated on an area of our network separate from where we store sensitive information related to you, our Cellcom/ Nsight family. We have no evidence that personal information related to you, your name, your addresses, your financial information, is impacted by this event.”
Cellcom initially claimed the disruption was caused by a technical issue, stating that data services, iMessage, RCS messaging, and 911 emergency services remained operational.
However, users became increasingly frustrated with the loss of service and the inability to port their numbers to other carriers due to Cellcom’s platforms having issues.
On May 19, Cellcom began bringing some of its services back online, including SMS text messaging and making and receiving phone calls to other Cellcom subscribers.
However, the company says that while they can’t promise when services will be restored, they are trying to restore full service by the end of the week.
“While we would like to provide a timeline for full restoration, we are unable to share exact milestones with complete confidence. Our team continues to build on the progress shared yesterday and our best estimate is that full service will be restored by or before the end of this week,” reads a service updates page on Cellcom’s site.
For Cellcom subscribers having issues recovering services, it is recommended that they enable airplane mode for 10 seconds and then disable it again. If that does not work, subscribers should power down their phones and start them up again to attempt to initiate services.
Yesterday, BleepingComputer contacted Cellcom with questions about the disruption caused by a ransomware attack or another cyber incident, but did not receive replies to our questions.
Cellcom CEO Brighid Riordan also shared a video for subscribers to explain the situation and what they are doing to recover from services.
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