Are you sure you're logging in to the correct account?
The fact that it's trying to sign you up as a new member means that either you're not logged in to the correct account, or that your account has expired (it needs to make an outgoing call or text, use the internet or receive a payment every 6 months to stop it expiring.
You should be able to use the password reset procedure to find your membername:
You'll receive an email and your membername will be in the subject.
Have you definitely used your phone for one of the above services in the last 6 months?