Nothing happens when I double-click any of the fields in Conctacts
(Phone, Mobile Phone, any other field). The same goes for the buttons
in front of the input fields. No pop up window, no options. Nothing.

My "Phone and Modem Options" control panel is set to:

Country: Finland
Area code: empty
Outside line: empty
Tone dial

There are no other options.

Is there really no way to turn this off?

I mean, gsm is the world's biggest mobile phone network standard and
Outlook in the year 2007 refuses to work with it's dialling prefix
standard?

That sound quite odd to me.

This is a real deal killer to me, if I can't change this. Will have to
dump outlook.