How can I locate the phone number of someone living in Germany who has recently changed their number?

I am trying to locate a friend in Germany who has changed their phone number. I have their old number. Also, is it possible to get a cell phone listing in Germany?How can I locate the phone number of someone living in Germany who has recently changed their number?
Here's a link that explains how to use the phone book web site for Germany:

http://www.numberway.com/phone-numbers/4