It sounds like you want to learn how to go about removing an associated device from an Apple ID. You can do so by following these directions:
- Open iTunes.
- Sign in to your Apple ID by choosing Store > Sign In from the iTunes menu.
- Choose Store > View My Account from the iTunes menu.
- From the Account Information screen, click Manage Devices.
- Click the Remove button next to the device name you would like to unassociate.
I had the same problem. I went to https://www.icloud.com/find and signed in. click find my phone then click all devices at the top and there will be a list of phones, you may click remove or erase and remove from your account. This worked for me.
I almost got my hopes up. And then I get the update software required. iCloud will only ever be available for those who maintain their gear with the latest operating systems, which pull at insecurites of the user suggesting that they are more secure etc. It's a pain in the butt when living in a developing country where a Software update will require a 6 to 8hr download and be successful only IF the connection retains its connectivity during that time.
We've bought the product, iMacs and iPhones, is that not enough? As it is I can't access any settings that allow me to desynchronize an iPhone from my iTunes Account. The novelty of using these systems and keeping up with the 'Smart' crowd is wearing very thin, the restrictions of the software manufacturer being anything but Smart in the first place...