Sign in icloud

You need to create an Apple ID some other way, because an iPhone can only be used to create 3 Apple IDs.

One way is to contact Apple Support using the Contact Support link at the top of this page. Here are other options—>How to create a new Apple ID - Apple Support. After you create it you can log in with it on your iPhone.

Perhaps this article will help:

If you see a Could Not Create Apple ID or Could Not Set Up iCloud message - Apple Support

or see the replies to:

can't create new APPLE ID - Apple Community