>You actually have to snail-mail them your resignation letter

So? You have to send written notice to cancel any contract in Germany. This is totally standard.

I would prefer to send them written notice about resignation rather than a call where they try and talk you out of it. I do the same with credit cards because you always get put through to the "please stay with us, keep your card, just don't use it" people who I don't wish to argue with.

Pretty standard. Try to find a "cancel my service" link anywhere on the Verizon or Comcast website. You have to call them, at minimum, and then as soon as your intentions are clear you will be transitioned to a "retention specialist" who will waste your time trying to talk you into keeping the service.