deleting membership (Bonn)

hi,

I want to delet my memnbership immediately before it renews tomorrow, and it is impossible to do it. Or it is hidden very much somewhere in this website, which is very outrageous and disappointing that internations try and make it so difficult to delete memberships. after this struggle I will definitely never going to pay for mebership in the future even if later I would come back.
Please someone tell me how I can delete it, or how I can delete my banking card data (that is also not allowed!!!)

Agnes