How to Stop a BlackBerry Syncing With Yahoo!
- 1). Scroll to the "Options" icon and press the trackball or trackpad.
- 2). Highlight "Mobile Options" and press the trackball or trackpad.
- 3). Change "Data Services" to "Off."
- 4). Press the Menu key. Highlight "Save" and press the trackball or trackpad to apply the selection.
Source...