AT&T’s U-verse TV and high-speed Internet service had been mostly restored in Charleston and other areas after being down for more than three days, the company said Thursday.

Customers will be credited based on the length of their outage, said Josh Gelinas, spokesman for the company’s South Carolina region.

AT&T blamed the problem on a software upgrade and apologized for the inconvenience.

Gelinas said it affected “a limited number of customers in some of our Southwest and Southeast region states.”

AT&T had 7.4 million U-verse subscribers as of the 2012 third quarter.

Dallas-based AT&T said it expects that any lingering technical glitches would be resolved quickly.

“We will issue credits to customers we know are impacted,” Gelinas said in a written statement. “Credits will appear on customers’ bills within 30-60 days. If they haven’t seen a credit on their bill within 60 days, they can call us to make sure they receive it.”

AT&T began rolling out U-verse in the Charleston region in mid-2010.