What is the definition of a Christian? Are mormons Christians? Many call themselves Christian, but Jesus says in Matt. 7 "Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven"
Even some universalists calls themselves Christians...
And the debate rages on - yes Mormons consider themselves Christian, for them I can see an argument for saying they are a distinctive Abrahamic faith in their own right due to additional material they report to be revealed scripture and the unique and distinct theology and worldview.
Since the earliest years of the church there have been universalists within the church, even some of the founding thinkers.
There were Christian Gnostics who supposedly believed in reincarnation. Some people have said they though Origen believed in reincarnation, but I'm not sure that is the case, more that he believed in the pre-existence of souls.
Conditional immortality is believed by some Christian denominations. Some but not all such denominations are non-Trinitarian.
Theologians of these denominations self-report being "more true to the bible than traditional Christianity" which of course traditional Christians disagree with.
(interestingly all of these various theories about the afterlife are considered plausible by some Jewish theologians)
Whether or not people "call themselves Christian" well, that starts going into discussions of things like self identification, labels, who accepts what label, how important is a label, who is a gatekeeper or authority for what the label means, and on and on.
And discussion rolls on...