Comcast’s data-usage meter gave thousands of customers inaccurate readings for two months because of a software bug, causing the broadband provider to incorrectly charge about 2,000 users for exceeding their monthly data caps. Comcast has admitted the error and told Ars it is giving refunds and additional credits of $50 each to customers who paid data overage fees that shouldn’t have been assessed.

We contacted Comcast two weeks ago after we heard from a customer in Duluth, Georgia, who found that Comcast was recording major data usage on his account even when he wasn’t using the Internet. The customer, Michael (who requested we not use his last name), supposedly had exceeded his 1TB monthly data cap. But when he unplugged his modem overnight, Comcast recorded another 40GB of usage during a 15-hour stretch in which he couldn’t have used any data.

Our inquiry to Comcast and complaints from other customers on social media caused the company to investigate. A Comcast spokesperson told us what the investigation discovered yesterday.