Perhaps I have not explained myself well...

In Spain Telefonica (the main telecommunications company) registers each telephone line to a single person, which is the one who pays it.

You may also know that in Spain young people lives usually with their parents even when they start to work.

Another interesting fact is that it is frequent that the first son is named after his father's name. In the States if you have a father called Mathew Smith a son with the same name would be called Mathew Smith Jr. In Spain someone called Jaime Muguiro y González de Castejón could have a son called Jaime Muguiro Domínguez (Domínguez being the surname of his mother).

Thus, this individual could be living in his parents house, in which the telephone line is obviously registered to his father's name and not his.

Sue: What I would do if I was you is calling the number I have written above and asking if they have a son called Jaime Muguiro Domínguez, and where can you contact with him.

Regards.

Fernando