Seems like you're being told to just grab the internet from one of the other flats. Assuming they're paying for it, they might have simply changed the SSID or password to stop that.

I believe Cablecom is cancellable immediately if you move. They answer phonecalls in English, French and German so it's worth giving them a call. If there's a socket in your room it could already be enabled - check this thread:

Internet for FREE (for everyone, provider Cablecom)