NAPLES, Italy — About 550 U.S. and NATO customers who are served by the Italian phone company Telecom Italia can expect credits in their phone bills this month, U.S. Navy officials said.

A routine audit by Navy Exchange personnel at the Naples store revealed customers were charged higher rates than those negotiated by NEX from November through April, spokeswoman Kristine Sturkie said.

"The store’s Services Operations Accounting Technician does checks and balances in all departments, including Telecom," Sturkie said.

Customers will receive a credit averaging $76 in this month’s bill.

The negotiated rates range from 5.5 cents per minute to 47 cents per minute, depending upon where in the world the customer calls, Sturkie said.

The erroneous billing stemmed from an information systems mix-up. As soon as the company was notified of the mistake, officials immediately issued credits to the bills, said a spokeswoman with the Telecom Italia corporate office in Milan.

Customers affected by the overcharges who already have moved from Naples on a permanent change of station can expect a refund, Sturkie said.

"The NEX keeps customers’ forwarding addresses and e-mail addresses on file when they PSC. According to NEX Naples, only 20 customers have moved," she said.

The NEX acts as a liaison between U.S. and non-Italian speaking customers and the Italian service providers, such as telephone and utilities companies.