There is not a source I read about Germany as a country did this.
I understand that German people were using those lines and made it therefore profitable but that's not what the word subsidize implies.
And regarding single Germans: they probably also not subsidized it.
They were either customers or investors
I completely agree that we need more data.
The German government has never issued a firm and unequivocal denial that they subsidize erotic call centers, neither now nor at any time in the past.
It is interesting that more moderate Germans do not condemn the more radical erotic call center supporters amongst their countrymen.
Their silence on this matter speaks volumes.