You have the consumer BlackBerry data plan, correct? And you added you yahoo email to the BlackBerry by entering the address and password either into the setup wizard on the handset or at your carrier's website. You would remove it same way. Go wherever you went before, and delete.
A hard reset is a battery pull. But it is accomplished by doing so with the power on, and wait at least 30 seconds.
You said you sent "service logs". First time through your post I thought you meant service books. Whatever, see How do I resend my service books? - BlackBerryFAQ
for instructions on resending service books.
Before you go to the trouble of deleting your address from BIS, you might simply try resending service books alone. Posted via BlackBerryForums.com Mobile