For complaints in connection with insurance brokerage, you can contact Versicherungsombudsmann e. V. (arbitration board):
Insurance Ombudsman e. V.
P.O. Box 080632, 10006 Berlin
Phone : 0800 3696000
Fax: +0800 3699000
Email:
complaint@versicherungsombudsmann.de
https://www.versicherungsombudsmann.de