Yes and no. There are other providers in Germany. However, with the EU's neoliberal privatization policy the governments privatized many existing infrastructure. Vodafone bought the previous government company that owned all of the the cable TV infrastructure of Germany. So they are a monopoly of a particular type of internet connection. Depending on the place the alternatives could be too slow since Germany also has an aging population that do not {care about, demand} higher internet speeds and didn't upgrade its copper infrastructure due to corruption.

Some new apartments also simply lack phone lines. No idea how that's legal (since there is no competition at all on DOCSIS, unlike on DSL, in Germany), but it's a thing these days.