Une Erreur

A man just called my landline. I could see a 0033 number so I answered with ‘Allo’. There was loud music playing. At first I thought it was one of my French friends but after a back and forth, I didn’t recognise his voice. He also sounded drunk. In French, I asked who he was. He asked me who I was. Eager now to get off the merry-go-round, I said, ‘Vous avez fait un erreur.’ He scoffed, then corrected my French, ‘Vous avez fait une erreur. UNE erreur.’