Cellcom Acknowledges Cyberattack as Cause of Prolonged Service Disruptions

Wisconsin wireless provider Cellcom has confirmed that a cyberattack was the cause of the significant service outages and disruptions that began on the evening of May 14, 2025. This incident resulted in disruptions to voice and SMS services, affecting customers across Wisconsin and Upper Michigan, and left many subscribers unable to make phone calls or send text messages.

Initially, the company described the issue as a mere technical outage. However, following mounting customer frustration over the ongoing service challenges, Cellcom’s CEO, Brighid Riordan, disclosed that the company had experienced a cyber incident. In a letter to customers, she emphasized that Cellcom had prepared for such situations by implementing established protocols and engaging outside cybersecurity experts. The company also notified the FBI and local Wisconsin officials and has been working tirelessly to restore services safely.

Riordan reassured customers that the incident primarily affected a segment of the network that does not house sensitive personal information, stating, “We have no evidence that personal information related to you, your name, your addresses, your financial information, is impacted by this event.”

While earlier communications indicated that certain services such as data services, iMessage, RCS messaging, and 911 emergency services continued to operate normally, users reported significant frustration due to the limitations on service and the inability to transfer numbers to alternative carriers.

On May 19, some services began to come back online, enabling SMS capabilities and allowing calls between Cellcom subscribers. Despite these improvements, the company could not provide a definitive timeline for the complete restoration of services but expressed optimism about resuming normal operations by week’s end. Riordan noted, “While we would like to provide a timeline for full restoration, we are unable to share exact milestones with complete confidence.”

For subscribers encountering difficulties while trying to regain services, Cellcom has recommended enabling airplane mode for ten seconds, followed by disabling it, or alternatively restarting their devices to facilitate the restoration.

In response to inquiries regarding whether the disruption was related to a ransomware attack or another cyber incident, Cellcom has not yet provided additional comment. CEO Brighid Riordan has also released a video update aimed at informing subscribers about the incident and the company’s response efforts.