Most phone, internet and electricity contracts in Germany have a cancellation period (Kündigungsfrist). If you want to end your contract, you must do it before that period. For example, you must cancel your Vodafone contract at least 3 months before it ends. Vattenfall has a Kündigungsfrist of 6 weeks. If you don't cancel your contract, it's renewed automatically for another year.

In some cases, you can cancel a contract early if there is a price increase, or if you move to an address where the service is not available1.

Rent contracts also have a Kündigungsfrist. The default is 3 months. It can be less than 3 months, but never more than 3 months.