Nightmare

I was initially contacted by Teranet with an offer of a free fiber optic (Glasfaser) connection. They canceled my original contract, opened a new one, and then attempted to bill me €350 for “planning fees” (“Planung”). I canceled the new contract the same day I saw this charge—back in February 2024. Since then, despite sending over 10 messages and receiving two official confirmations that both contracts were closed, they continue to pursue me for the €350 fee. I’ve sent messages, even handwritten letters, with no resolution in sight. No replies, repeated delays—just more bills for a contract that should be long closed. How can I stop this? Who can help? upd: people, check the answer and keep in mind that I received the bill the day before. They also put my name in the answer. Total incompetence... ... total ...