You can delete any Yahoo! ID from your Messenger List by sending a text message in the following format:

delete Yahoo! ID

Then send to your corresponding wireless carrier number as shown below.

All (Supported) U.S. Wireless Carriers—92466

Rogers—92466000

All (Supported) India Wireless Carriers—8242

TMTouch—1777

Maxis—32235

SMART—2580

GLOBE—22580

M1—8881

DTAC—192466

TELKOMSEL—4246

EXCELCOM—9246

STARHUB—0903