Setting up the various services you use for this automation can be intricate. You might use several different services at any one time, and you might have forgotten to record all the details of every service, or have forgotten even having set up a service.
That is - my blog posts are autoposted into a Facebook page using dlvr.it. Somehow those Facebook page posts were then posted to Twitter. The question was - How?
Several times now I've looked and looked all over Facebook trying to find where I'd configured the Apps connected to my Facebook pages and my personal profile. I vaguely recall setting up Apps like RSS Graffiti, which used to be an excellent tool for autoposting from an RSS feed onto a Wall (like a Page). RSS Graffiti has since shut down, and in any case I supplanted that functionality using dlvr.it. But somehow Facebook was still posting to Twitter and maybe there was some kind of zombie corner of Facebook where some app or other had been configured and then forgotten.
I don't know if that's the case, I was unable to find where this configuration would have been. I even reviewed all my dlvr.it accounts to see if any somehow had something configured for a Facebook page. No joy there.
I finally had a brain cell click together, and realized that in the Twitter settings are "App Approvals" for every app that you've agreed to give access to your Twitter account. Perhaps, I thought, there'd be a listing for a Facebook something or other that could be revoked. And sure enough, there was.
You reach this list of approvals through the Twitter account settings page. Simply look for Apps on that list, click on it, and you'll see all the App's and websites you've agreed to grant access to your account. If you're like me, the list is VERY LONG.
Look for a Facebook-owned app named "Facebook To Twitter". Revoke the access of that App. Done.