In fact, for some months I was getting two giant envelopes regularly, as NTT reminded me over and over again that they were switching to a new billing system run by the newly established company NTT Finance. (Further thinning the guise that the NTT telephony monopoly was ever really broken up in Japan...)
So the other day I signed up for NTT e-statements. It's a pretty easy procedure, and it knocks a simple 100 yen off of your monthly bill. Since you're probably roped into a 2-year contract with them anyway, in the long run that's about $30 saved.
To do this, you can still contact a representative at NTT East's @Billing service or NTT West's MyBilling service, but since all the financial transactions of both are handled through NTT Finance now, that's ultimately where you'll end up. So on NTT Finance's site, hit the apply (お申し込み) button and fill in your account information.
A word before beginning the application: You have to be paying by automatic bank withdrawal (口座振替) or credit card to be able to switch to e-statements. If you pay for your NTT service in cash by taking the bill to a convenience store, you'll have to switch to another payment method first.
To fill out the application page, you'll need:
Your account number (if like me, you don't have a home phone and just use NTT for internet service, you'll write "00" followed by the ten-digit 請求番号 that appears on your bills)
The name and address registered on your account
Your daytime phone number
After you fill this info out, NTT Finance will contact you by telephone to confirm your request. The postcard detailing your login info and change to e-statements will come by mail a week or two later.