I've had experience of this and it can be scary at the time.
My dd1 had a man with two cats come some evenings when she was in bed to "talk" to her.
She didn't mind this so much but talked about two cats that came with him. (yes I know I sound like a crackpot but bear with me).
She described him in extreme detail and it sounded like my (ex) husbands great uncle - we haven't any photos of him at our house or his parents, so it couldn't have been guessed.
Then she started drawing other children and adults that would "talk" to her at night, she did this at nursery and would tell the staff about them - she was about 3/4 at the time.
I too, didn't want to make this in any way real to her so listened to her in a half hearted way but was trying to take it in at the same time.
Then she said that the little boy wouldn't leave her alone - she said he wouldn't let her sleep and kept moving her things around - we never saw any of this.
Anyway, I had a friend who went to a spiritualist church - she had been going for a couple of years because she was interested.
My husband and I discussed this and agreed to ask her for advice. We made sure she came around when my daughter was asleep so she didn't know anything and then she lit a candle in the living room and (not out loud) asked them to leave. They did apart from the little boy (apparently) and both my husband and I heard a bang from upstairs and there was no-one there as my daughter was downstairs asleep.
My friend persevered and then she said they had gone - we watched the candle moving quite a lot (I know that can be explained away too)
Anyway, that seemed to do the trick - we had already done the talking to our daughter about there being no-one really there but she was insistent that there were people coming into her room at night. It had been disruptive because she kept waking up throughout and was generally tired then during the day.
I don't know how I would have gone about it if I hadn't known my friend would help, although she did suggest that if it didn't work then one of her friends from the spiritualist church would help - at no cost either.
I would suggest that you maybe talk to some friends who may be able to give you a recommendation - they should be at no cost - rather than a charlatan who would probably charge.
It's not easy - it's a taboo subject and unless you've had experience of this it's easy to disbelieve.
However, when we had the issue I think I would have tried anything to have peace of mind - as long as that didn't involve the child in any way - I didn't want her growing up believing in ghosts or anything like that - imagination can be a powerful thing.
Anyway, I hope some of that helps.
Good luck