An IT security drill went off the tracks in Belgium, prompting a regional government office to apologize to European high-speed train operator Thalys for involving it without warning.

Belgium’s Flemish regional government sent a mock phishing email to about 20,000 of its employees to see how they would react.

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The email purported to be a booking confirmation from Thalys for a trip from Brussels to Paris, including a stay in a fancy hotel. The cost—almost €20,000 (about US$22,000)—would be charged to the recipient’s credit card unless the person cancelled within three days, the email said. To cancel the trip, the email instructed recipients to send their credit card information to Thalys, Belgian media reported.

Rather than hand over such information, though, government employees started calling Thalys to complain, to the bewilderment of its staff: The government had neglected to inform Thalys of the drill and nobody in the company’s call center knew what was going on.

Some government employees also reported the matter to the police.

Frank Geets, the Flemish government’s administrator-general for facility management, said the government went a bit off the rails by not informing Thalys of the drill.

“We made the mail as realistic as possible and used Thalys’ logo. But actually, we did not have their permission to do so,” Geets told Flemish news channel VTM, adding that the government has apologized to Thalys for “being a bit overzealous.”

While phishing attacks against staff are a perennial problem for large organizations, training to defend against them needs to be done with care and forethought. The Flemish government is not the first to discover this: An anti-phishing exercise by a U.S. Army commander went farcically wrong last year.