First check whether it makes more sense to switch to a tariff without an on-going charge (Basic tariff). So you can continue to use book-n-drive if you need a car again. You will find the appropriate tariff change form in the download area.
If you are sure that you no longer wish to use book-n-drive, you can cancel your contract with six weeks' notice to the end of the quarter. Please send us your signed cancellation by letter, fax or scan to our service office in Wiesbaden (Rudolf-Diesel-Str. 5, 65719 Hofheim am Taunus, Fax No.: 0611 - 77 8 77 94, firstname.lastname@example.org ).