I went to Nuremberg this summer already planning to travel to the Harz mountains in September. I got my rail ticket for September at the station in Nuremberg, wanting to avoid having to print the ticket out at home. Unfortunately, I had to change the first day of my holiday. I telephoned DB's English office - sorry, you need to talk to DB Germany, here's the secret trick to get an English-speaking operator. Phoned DB Germany and discovered that they can only change tickets purchased by phone or online, if you want to change a ticket purchased in a ticket office you need to go to a railway station. Unfortunately I'm still in the UK, so I've had to pay full fare for another ticket.