Yes... I have had enough otherworldly experiences to know that another plane or dimension exists. Given that, there are entities who are attracted to the higher vibration of psychic people and who come across as guides, deceased relatives and angels. There's a guy in Australia named Robert Bruce who has a website http://www.astraldynamics.com
he talks about such entities and has a couple of books on psychic protection. It would be worth checking his site out. I believe that if you ask if this voice is from the light, (Robert, I think talks about doing just that) if the entity is not on the up and up, it cannot say yes. You then ask it to leave and it must comply according to certain natural laws. I'm flyin' by the seat of my pants right now, relying on things I've remember reading. He has a forum on his site and you can post your question there too.
He also has a tutorial called the New Energy Way (I think) that walks you through raising your vibration. That is what you need to do.