AT&T announced Sunday, Feb. 25, that it would offer a $5 service credit to some customers affected by last week’s cellphone service outage. The outage, which lasted more than seven hours, impacted over 70,000 users, the company disclosed in a letter to employees.

According to AT&T, the disruption was caused by an incorrect procedure during network expansion efforts, eliminating the possibility of a cyberattack.

“No matter the timing, one thing is clear — we let down many of our customers, including many of you and your families,” AT&T CEO John T. Stankey wrote. “For that, we apologize.”

The company specified that the $5 credit does not apply to AT&T Business, prepaid, or Cricket Wireless services. Customers eligible for the credit might wait up to two billing cycles for it to take effect.

“This is not our first network outage, and it won’t be our last – unfortunately, it’s the reality of our business,” Stankey wrote. “What matters most is how we react, adapt, and improve to deliver the service our customers need and expect.”

Last week, the Federal Communications Commission announced it was investigating the incident. Meanwhile, the U.S. Cybersecurity and Infrastructure Security Agency is collaborating with AT&T to determine the cause.