Are you trying to make us believe the Christian religion, or any religion for that matter, doesn't have a basic set of beliefs its believers follow?
Have you ever looked into what those believers think about ghosts?
Catholics have purgatory. Some believe that purgatory is here on Earth, and that explains ghosts. Completely compatible.
Others Christians believe that it is some type of time-continuum phenomena where the events of one's life keeps replaying over and over again, and thus explains ghosts. Completely compatible with Christianity.
Other Christians believe that there is a time-lapse before going to heaven. The Bible mentions that the first will be the last and the last will be the first. Some sects believe that the last Christian (either to die, or to convert, not always the same with all) will be the first to enter Heaven after the final judgment. Until then, some souls roam the Earth, until the time in which Jesus has his second coming (this belief is more predominant among the apocalyptic Christians) and again is completely compatible with Christianity.
Other Christians believe that it is possible for one to be saved from hell. TBN actually had a story about an individual (a Christian) who was compelled by God to pull tortured spirits out of hell as they had repented of their sins. There is no evidence in the Bible that says this would not be possible, and is still compatible with Christianity.
Now, when I say Christianity, I don't mean the entire religion as that would be senseless to do. Christianity is extremely diverse, and has many different beliefs. Some Christians believe that every soul that goes to heaven or hell becomes a angel or demon. This would also explain ghosts.