How do you get rid of ghosts on the Sims3?

Chicken Nugget: I have a house in Riverview which came with three ghosts. The first day or two after I had moved in another sim offered to remove my ghosts for me. I said yes and she promptly had them expelled. The ghosts did not appear for away, so I left the tombstones in the yard because I thought they had character near my garden. Then I noticed one of the ghost show up for a couple (sim) hours. She used some of the house items, possessed the television, then took off. The next night another one the ghost appeared and did similar things before leaving.

Do I have to have the tombstones removed from my yard to keep this from happening? Or is there another way to have the ghosts permanently removed?

• Sims3
• pc games
• ghosts
• riverview