And in what context? I'm afraid without some more info none of what you say makes any sense...
I have a tablet and a smart phone. I get EPub e-books out of the library. I can ready them fine with Overture on my tablet. When I try to download a title to the smart phone, I get an "Abode ID" error. Further information says that the smart phone Abode account data is different than the tablet Adobe account data and that they need to be the same in order for me to download the title onto my smart phone. Hope this helps.
You might get better help in the Adobe Digital Editions forum. I would expect that you need to ensure your Adobe Digital Editions username and password are the same as the ones used on Overture.
Moving this discussion to the Adobe Digital Editions forum.
It depends on the app running on the smart phone, but it should have a deregister option somewhere.
Hunt around in the app.
Also settings like this are sometimes separated from the app itself in a separate settings control with subparts for each installed app.
Once it is deregistered, you should be able to reregister with the AdobeID you want.
If you say exactly which phone and which app someone may be able to help with more details,
or search google for something like 'appname deregister DRM' (replace appname with the name of the app you are using).