Who was it?

Security in my building is pretty tight. It is not as tight as it was in my building in Sao Paulo when a group of security guards spent ten minutes analysing a letter with my signature on it authorising entry for a friend who had been staying at my place for a month, but it is tight nonetheless. No one in Brazil has the key to the front door of their building. Access is only by being buzzed in by the security guards. Visitors must present themselves at the door and the guards phone up to the resident to obtain permission prior to letting the person in. Here it is a little looser as the guards sometimes let in my regular friends without calling up, but still, people don't usually get in without prior permission. This afternoon, I left work a little early to finish packing my bag. Just after 2pm, the internal phone rang and it was the guard requesting permission for someone claiming to be a carpenter to come to the apartment. Neither expecting nor having requested a carpenter, I asked for the person's name and what sort of work they were expecting to do in my apartment. The answer came back that he was a carpenter. No name. No workplan. So I refused entry. I wonder who it was.... Mistaken location? Or something else? Thank goodness for the interfone!