Germany is a conservative, backward shithole, so good luck.
1000 EUR is steep though, maybe see if you can negotiate it down to 100-200 and just pay it? Or just ignore it and see if they actually go to court.
It’s an awful situation though. I had O2 there destroy my credit score after I closed my account (which could only be done via fax - lol Germany) and left the country, but they were still trying to settle the final month’s payment of ~20 EUR for over a year.