How dare ATT enroll me in paperless billing when it was not asked for.

Good point.  

No bill = no payment due?

That like the old joke, "how can I be overdrawn?  I still have checks left."

This is why I like auto pay.

This thread was clearly not started to discuss the relative merits of paper vs. paperless billing. Surely there are many threads dealing with that subject.  Paperless clearly has many benefits.  But again, a particular person's preference for paperless is irrelevant here.  That you seem incapable of understanding of why a person may prefer paper is fascinating, but also irrelevant.  The issue of this thread is AT&T's unscrupulous practices in attempting to evade responsibility to customers by converting paper bills to paperless without prior consent.

@Footay AT&T has no interest in if you have paperless billing or not. As has been stated the OP at some point in time opted-IN and has simply frogotten about doing so. There is no benefit to AT&T to opt  people in w/o their consent.

Think of the positive affect on the environment though!

You really can't understand why AT&T sees a tremendous cost savings by not generating and mailing paper bills?  Unless a charity performs this process for AT&T, the first sentence of your response is absurd.

The issue of whether the OP was opted-in is not in doubt.  But that is not the point.  The point is consent.  No one, other than the OP can possible know with certainty whether the OP intended to request paperless billing.  Other posters can only speculate all day long.

Finally, there is absolutely a gigantic and irrefutable benefit for AT&T to opt people in w/o their consent.  Only a portion of those victims will choose to request a paper bill.  AT&T gains a cost savings for each person that doesn't request a paper bill.

AT&T's account management system ABSOLUTELY WILL auto enroll your account for paperless billing.  The big problem is they don't tell you when they do it.  But if YOU choose paperless billing then you should get an email confirmation on it.

The current default is as written in the terms of service, paperless bill

Notification is sent to both to my email and I get a text when my bill is ready and another when it is paid by auto pay.   

Save a tree folks.  Wireless bills are many pages long.  Mine is typically 35 pages or more.

Here it is in the terms of service:

https://www.att.com/legal/terms.wirelessCustomerAgreement-list.html

How Will I Receive My Bill? What Charges Am I Responsible For? How Much Time Do I Have To Dispute My Bill?
You will receive an electronic (paperless) bill at AT&T's online account management site unless you tell us you want a paper bill. You will be given the option to choose electronic billing or paper billing when you purchase service. Each month we will send you an email notice when your electronic bill is available online. This will be sent to your official email address on file with AT&T. You are required to keep your email address current and to notify us immediately of any change in your email address. You always have the option of switching back to a paper bill by changing your billing preferences at AT&T's online account management site. You will not receive a paper bill in the mail unless you expressly request one.

You are responsible for paying all charges for or resulting from Services provided under this Agreement, including any activation fee that may apply to each voice or data line. You will receive monthly bills that are due in full.

The problem isn't choice I can choose to have paper or paperless billing.  The problem is coercion.  I have always chosen to received paper bills and will continue to do so.  However, when the nag screen asks you each and every time you log in to your account if you want to switch to paperless billing and each time you are FORCED to choose the "No Thanks" option there is a problem.  Furthermore, when the "system" eventually learns that you are not going to willingly change your mind and therefore automatically enrolls your account into the paperless billing option anyway and doesn't tell you about it, THAT IS A PROBLEM!!!

I get asked something each and every time I sign in because all of my devices are paid off in full. 
so what?

Its advertising.....

This is what I get today, when I login, then when I request to see my wireless bill.