I am lucky: Somebody called me on friday, asking for Monsieur Grant.

It appears that my mobile number was previously that guy's. I got Monsieur Grant number, and called him. I got his father after a few tries, and explained him the situation. His answer was quite funny (imagine a strong contryside speaking):

"Ah oui... Quand il y a un problème, je me fais appeler chez moi, mais si je ne réponds pas, c'est renvoyé vers le portable. Je vais essayer de supprimer ça, mais c'est très compliqué, alors je ne sais pas si je pourrai le faire rapidement. Peut-être fin de semaine prochaine?"

"Hum... I see... When there is a problem, there is a phone call to my home, but if I don't answer, the call is forwarded to the mobile phone. I will try to change this, but it is very complicated, it will take time. Maybe end of next week?"

Apparently he still did not do it, as I was called this week-end during the night ;-)

Come on, Monsieur Grant! Read the f... phone documentation, or call France Telecom, or ask a friend to help you, but do it!