Customers of Verizon Wireless in Montana and Northern Wyoming were without service for more than seven hours Sunday morning.
The outage occured at 1 a.m. when a switch failed during regularly scheduled maintenance to the network, said Verizon spokesman Bob Kelley. He said Verizon's network team normally does updates early in the morning when traffic is light and customers are not impacted.
Engineers worked several hours to identify and fix the problem, Kelley said.
"Normally this maintenance and software update doesn't affect the network," Kelley said.
Interruptions in service were reported across the state after 1 a.m. Cellphone calls could not be completed and text messaging was compromised.
Verizon engineers told Kelley that service was restored at 8:30 a.m.