Here is a translation of the text from the DT website. The text covers what they expect in the event of a customer leaving Germany.
"I am moving abroad. Do I have a special right of termination?
Yes. If you move abroad, you have a special right of termination according to § 60 TKG (Telecommunications Act). By law, you are granted a period of one month to the end of the month.
Different regulations apply to your contracts with us:
The statutory notice period of one month to the end of the month applies to your mobile phone contract.
For the landline connection , we grant you a shorter period of six working days.
We need one of the following documents, as proof:
- De-registration certificate from the registration office
- certificate by the employer
- marching orders (for soldiers)
Use the landline / internet or mobile phone termination form and add proof as an
attachment."