Mick,
Its Invalid To Say Christians can't Be Mediums.
Christianity warns Against Mediumship And The Like, Because For Christians, This may Lead Followers Down A Path Opposit Of Christian Morals And Away From God (this Is True For Anyone - Any Of Us Could Follow A Dark Path, If We Chose To). But I Have Never Read A Passage That Forbids Anything. For Christians (and All Of Man) Are Given Free Will.

**if Mediumship Has Been Forbidden, A Preacher Is Probably The One Who Forbade It, And That Would Be Inappropriate For A Man To Speak For The Christian Version Of God
I Have Not Read The Entire Bible, So If You Can Direct Me To A Passage That Forbids Mediumship, I Will Eat My Words.

-SERENITY AND LOVE