About 500 Questar Gas Co. customers underbilled because of erroneous automated meter readings are getting both a Public Service Commission investigation and another apology from the company.

The commission said this week that it has opened a formal investigation to resolve the matter, caused by errors from an automated meter reading device called a transponder. The customers were underbilled a total of about $500,000.

The commission is asking the state Division of Public Utilities to conduct the investigation, with help from the Utah Committee of Consumer Services, and wants the division to recommend how to resolve the issues.

The commission said it will consolidate all the complaints into one docket. The commission will have a procedural conference at 9:30 p.m. April 17 at its office in the Heber Wells Building and is encouraging affected parties to participate in the process.

Questar this week is mailing letters to affected customers. "I want to apologize for the inconvenience and frustration caused by a bill sent to you that reflected an adjustment for an underbilling that occurred on your account," wrote Questar's executive vice president Ron Jibson. "This issue regarding an inaccurate transponder that was placed on your meter was not handled in a manner that reflects our standard of customer service."

Questar spokesman Chad Jones said customers originally were notified on their bills, which contained a past-due amount and a note at the top of the bill that explained the reason for it. They also received a letter a few days later.

Both the commission and company this week noted that customers do not need to make payments on the underbilled amount until the commission's investigation is complete. Michele Beck, director of the Committee of Consumer Services, said Monday that people should be informed that utilities "are not automatically entitled to recover all costs from ratepayers for unjustified mistakes."

The commission noted in a news release that customers must pay all current undisputed amounts. Depending on the commission's orders, customers who already have paid underbilled amounts could receive a refund, regardless of whether they have filed a complaint about the matter.

The commission directed additional customers with underbilling complaints to contact the Division of Public Utilities at [email protected], 801-530-7622 or 800-874-0904.

E-mail: [email protected]