I had an unusual request, earlier today. The user was worried that somebody was joining their Lync conferences, anonymously, and they wanted to change their conference ID.
I have never done that before, but found out it is pretty easy to do.
First, go to https://dialin.YourSipDomain.com, and it will take you to the Dial-in Conference Settings and PIN Management page, as shown here.
Then, after you click the Sign In link, it will take you to this screen. You can either click the Sign In button, and it will use your current credentials, or you can click the Sign in with a different account link and use those credentials.
If you don’t have a PIN already set, you will be prompted for a PIN, otherwise, go to the section for Assigned Conference Information section and click on the Reset my Assigned Conference Information link, and it will create a new conference ID for you.