You can contact the regulator at the following address and I would send a copy of your letter to them:
Luftfahrt-Bundesamt (LBA)
DE - 38144 Braunschweig
Tel.: +49 531 – 23 55 115 (mo-th 9-16, fr 9-15)
Fax: +49 531 - 2355707
fluggastrechte@lba.de http://www.lba.de