This is not the correct place to terminate a contract. You also shouldn't post personal information in a public forum!

If you want to terminate your contract you can do that here: http://info.o2online.de/kuendigung/

Be aware that the contract will not end immediately but at the end of the contract term.

Welcome to the community .
bs0 was already kind to give you the right info for the termination.
Have you already been able to submit the cancellation by using the link?
And did you already receive a confirmation from us with a specific date?
Best regards and many thanks for your support.
Steffen