I have seen TV documentaries about this kind of hearing voices. It is caused by the different 'neurotransmitters' (chemicals everybody has in their brains). If these brain chemicals are not in the right measurements - too much serotonin or too little dopamine maybe - it affects how your brain constructs how it sees/hears the world.
You need to see a brain expert doctor to work out which neurotransmitters are causing the 'voices'.
Just remember - ignore the voices - it is just your brain creating them - the same way we all create dreams when asleep.
One thing you could try - write down on paper all your thoughts/worries/plans/lists of things to do etc. I have always done that for no reason - just my thing - but now I have realised that it helps to empty out my head - because my brain can relax safe in my knowledge I've written it down and don't need to try to remember it.