We'll write your wilhelm.tel cancellation in proper German, send it the way that proves it arrived, and chase them if they go quiet.
Your last wilhelm.tel invoice, and that's usually it. Your customer number, the line being cancelled and the address they have on file are all printed on it, so we read them off rather than asking you to go hunting.
We use whichever channel gives you the strongest proof it arrived, which is usually the provider's own cancellation button. German law treats that as received the moment you click it.
You can usually get out early. German law lets you end a telecom contract when you move abroad and the provider can't follow you there, with one month's notice counting from the day you go. Telekom names military transfer orders as accepted proof, and other providers generally take them too.
We only ever need one page of your orders, the one showing your departure date. Everything else is blacked out on your own device before anything leaves it.
The rented router ends with your contract, but it was never yours. If it doesn't come back they'll charge you what a new one costs, so it's worth posting before you fly.
The final bill usually arrives several weeks after you've gone. If your German account is closed by then the payment fails, and unpaid bills here are passed to collection agencies fairly quickly.
Extras have their own rules. A phone you're paying off monthly is a separate purchase and carries on regardless, and a TV package added later can have a minimum term that outlasts the main contract.
It's better in German, because that's what gets acted on without argument. We write the German and show you an English translation of every line, so you know exactly what you're sending before you send it.
Not at all, and you're not unusual. U.S. forces members are exempt from German registration, so most never had anything to deregister from. Your orders do the same job.
One letter covers all of them, each named with its own reference. No need to send a separate cancellation per contract.