Sale has ended but you can still get this app.
Download Zielnetz Flatrate Networkscan Now
Zielnetz Flatrate Networkscan

Official Description

Shows the mobile network (D1, D2, ..) + provider (Aldi, Fonic) of a phone number, even after porting.Scans nr or whole phone book and stores the result in your telephonebook. Save money with phone flatrates.No surprises on the invoice anymore.

*Only for Germany*

Keywords: Query which network mobile operator