There are so many published accounts of this sort of thing, why ask here?

And why restrict yourself to voice communication; many communications have another form. A friend of mine has talked about that when her son wants to let others know he is there, they see a bluebird.

HEre is a link to a book that has many such communications (else where on this site)

http://afterlife-knowledge.com/cgi-bin/yabb/YaBB.cgi?num=1281547669

Why would you assume the person is asking for help? Maybe they just want to say hello, or just want to smile at us forbeing so confined in our ideas about reality.

I found this interview and thought it might be relevant if you want to try to communicate yourself:

http://www.bestpsychicmediums.com/Michelle-Article.htm