Who is really suffering in Hell and Enjoying in Heaven?

When a person dies, s/he goes to heaven or hell based on present life karma and any past karmas. In Buddhism, if there is no soul, who is punished in hell and who enjoys in heaven? as there is no physical body to feel pain and pleasure. If that person has learnt the art of detachment, how can s/he suffer/enjoy in hell/heaven? Does different realms really exists and do we travel through them?