You can find Erich Artur Matz in the 1940, 1941, and 1942 General Government Telephone Directories (Amtliches Fernsprechbuch für das Generalgouvernement). Search for:
These directories are hosted by the Municipal Public Library in Radom, and their website can be quite slow. It might take a minute or longer for the image to open in your web browser.
There are no entries for the surname Matz in the 1939/1940 or 1938/1939 Warsaw directories.