You can change your Yahoo! Music Unlimited service using our online service page. Depending on your level of service, you may be able to downgrade or adjust services on your own. Here's how:
In the Yahoo! Music Jukebox, click My Account in the top left corner
Click View Subscription History
Sign in when prompted
On Service Summary, click Manage Service
On Service Details, click Edit Service
On this page, you will be shown any options available to you for self-serve account updating