Oh, actually it started with incompetence, too: I wanted to order the BahnCard25 but payment didn't went through (and thus, I did not finish the order process). When I tried again, the coupon that I wanted to use for the Bahncard25 was exhausted. (which is why I went for BahnCard50 afterwards)
And why did I cancel the subscription anyway? Because the trip that I planned (Hamburg to Paris) and that was listed as buyable was of course everything but buyable. Always failed at the last step of ordering with some indistinct error message. Well, they really did not want my money, that much I can say.