A gas station in central Vietnam had its license suspended for one month after officials discovered it had been charging customers more than allowed, local media reported.
The station in Nghe An Province's Nghi Loc District was also fined VND20 million (nearly US$1,000) for the violation, a source from the local market watchdog agency told Tuoi Tre (Youth) newspaper.
Officials said they acted upon tips from enraged customers.
Vietnam's government still has complete control over market prices of some products, including electricity and fuel.
The price of 92-RON, the most popular gasoline grade in Vietnam, was reduced from VND18,100 a liter to VND17,920 on January 6.
But three days later, the station was still selling at the old price.
Hoang Cong Suu, the 75-year-old owner, said his eyesight was poor and he thought he had already changed the price in the fuel dispensers.