I changed internet providers and now I am being asked to contact my internet provider to change yahoo password?

I have my computer set to auto fill my accounts with user ids and passwords. I forgot I had changed my Yahoo account and filled in the information manually with the incorrect password. The auto fill in saved the wrong password and now I can not access my account because the correct password has been overriden by the incorrect one. When I try to access my account to change the password, I am told I need to contact my internet provider in order to change the password, I no longer have SBC global or AT&T service and my current internet connection is with Alltel wireless and they are not able to help me. Any ideas please?