Yahoo! seems to get a kick out of making it as hard to find their phone numbers as possible.  After several hours scouring the 'net, I located 3 phone numbers for Yahoo!.  Two are for customer service, and one is for billing issues.

These ever elusive phone numbers are listed below.

Customer Service:  +1 866-562-7219 (US Callers Only) Their hours are 6AM - 6PM PST (PDT)

An alternate is: +1 866-562-7228

They have a seperate number for billing issues: +1 800-318-0631

Happy Hunting!