Mediums will not get rid of them forever. They'll come back. They will get violent, disgusting and vile. They always do.
Letting Jesus Christ into your home and heart gets rid of them, because to be very blunt about this, these things are really just fallen angels. Demons. Pretenders.
I used to watch Ghost Hunters, Ghost Adventures and stuff like that. Then I ran across a Christian who told me about this aspect of shadow people and ghosts, that I never really thought about.
Why are they here, if they ARE fallen angels?
They're spirits, and have nothing else better to do, but try and deceive us of the truth. They don't have to eat or sleep, and are restless in their efforts to deceive people. Their mere presence gets us to question what God said, because if there is such thing as an afterlife and the only two options are heaven and the "other place", then these "ghosts" and "shadow people" aren't following the rules. So what are they?
If you have time and aren't convinced of what I'm saying, then hear it from other people:
Laura Maxwell (ex-spiritualist) - "What are ghosts, spirits or other earth-bound spirits?" (~23 minutes long)
FaceLikeTheSun - "The Truth Behind Ghost Hunting" (~15 minutes long)
Just remember, if it's something paranormal or supernatural, how do you know if you can trust it?
They know the name of Jesus. They tremble and fear that name. I'll be praying for you.