By Katie Lannan

More than 50,000 National Grid customers will receive refunds or credits after they were improperly charged reconnection fees for their gas service, Attorney General Maura Healey announced Tuesday.

The refunds are part of a $7 million settlement Healey's office reached with National Grid, which also includes $3 million that will be used to help Massachusetts customers with their gas bills, $180,000 to the state's general fund, and $20,000 to defray the cost of Healey's investigation.

According to the AG's office, from 2010 to 2016 National Grid improperly charged 53,000 residential customers a $50 reconnection fee after their gas service was shut off for non-payment.

Many of those customers paid the fee multiple times, resulting in over 76,000 improper assessments. One low-income resident was charged the fee 13 times, Healey said.

National Grid agreed to eliminate the fee in 2010, and attributes the continued billing to a coding error in its system, Healey's office said.

The settlement also calls on the utility to improve its processes so similar billing system errors do not happen in the future.

Current and former National Grid residential gas customers who believe that they were assessed a gas reconnection fee between November 2010 and November 2016 and who have not already received a bill credit should contact National Grid at 1-800-233-5325 within one year to obtain a bill credit or refund from the company.