Just open internet explorer, click on Tools, then internet options and remove att from your home page and that should bring back your old home page. It worked great on mine. I hope it works for you.
I did that a couple of days ago.So far,so good.Hope we can keep it that way.I also wrote them and complained.
I hope that you didn't mention in your complaint that you can still access the old ATT/Yahoo! portal site using »my.yahoo.com because that would probably just inform them that they forgot to kill that backdoor entry point. -- We can never have enough of nature. We need to witness our own limits transgressed, and some life pasturing freely where we never wander.