I was after a long search for a cheap mobile operator now opted for "DeutschlandSIM" in tariff S (Vodafone network). ... - And I regret it in any way! Class service that responds quickly to questions, my number portability has went smoothly overnight and what was very important to me, I am now on the Vodafone network!
The non-existent minimum contract duration completes the package overall to a "5-Star I like this" Recommendation.