How expensive is the basic supply? Do you know that? Is it worth jumping into the triangle now and somehow getting active?
You have to research that with your provider. It varies locally. I would research that, the cancellation came now just in time for the heating season.
We were with Grünwelt for 5 years - we didn't have anything like that. Everything was fair and consistent.
I have been there once as well. In my perception, Grünwelt is a typical brand that tries to be "on top" in the result lists of the portal through bonus systems. But the bonuses are only given in the first year, and if you don't cancel in time (or only consider the first year in the comparison with two-year contracts), you can be wrong. However, it is often the case that if you don't feel like provider hopping anyway, you can disable bonuses from the search, and oh wonder, providers often have tariffs that are almost equally expensive but don't participate in this whole bonus fuss.