Siri does not dial short numbers in Switzerland?

Siri is not able to dial the number 1145 in Switzerland when stored in Contacts.

I can call the number when i tap on the number stored in Contacts. But when I ask Siri to dial it for me, Siri says: "Calling Auskunft" (so Siri recognizes which number to call). But shortly afterwars, Siri answers with "Sorry [name], I can't call Auskunft."

Problem existed with iOS 5 and still exists with iOS 6.

Dar Apple, is there an explanation for this behaviour?