The directions to Hauptstadtrepraesentanz Deutsche Telekom are here.

Berlin Representative Office
of Deutsche Telekom AG
Französische Straße 33a-c
10117 Berlin

The following websites might be useful for planning your trips:

For public transportation, check out http://www.bvg.de.
For citymap, please go to http://berlinonline.de/citymap.
For a brief visitor guide, go to http://www.berlin.de/english/index.html.