12.1
Changes or additions to this contract - especially to this written form requirement - are valid only in written form.

12.2
All explanations can be directed on electronic way to the customer. This is also valid to accounts within the contractual relationship.

12.3
Are or become single regulations of these general terms and conditions ineffective, the effectiveness of the other regulations is not thereby touched. To the place of the ineffective regulation answers the regulation, which is approaching to the economical purpose of the arrangement.