Réclamation pour produit défaillant

Dear [Mr or Mrs or Sirs],    We have purchased [produit] from you on [date] and have the regret to inform you that until now, it has never functioned as expected.  We remind you that we insisted on the point that it should [spécifications de fonctionnement] and that you ensured us of its compatibility with [produit].    We trust you are fully aware of the inconvenience this causes and that you will [action requise] with no delay.    We thank you in anticipation for your willingness to put an end to this situation and look forward to hearing from you    Yours sincerely  [votre nom]  [votre fonction]