If a person talk and answer himself in the mind only, answering with a different voice Is it a mental disorder

depends....sometimes i answer my own question in my mind...i am not sure if i use a different voice though

do you ever talk to others? even though that sounds weird i'm sure it's not that uncommon. most people just don't admit it. i don't know how bad it is but i don't really think you have a mental disorder.

crazy people

Not necessarily. People who had a large influence on you when you were young can leave lasting messages in your subconscious. A phrase or voice from your past very well can pop into your mind when you think about things.
You may have issues to resolve with these subconscious thoughts. If the person was abusive or negative to you and it continues to pop into your thoughts you may have to tell 'the voice' to shut up.
Or, it can be the voice of someone who comforted you, telling you to be strong. A keeper in my opinion.

May be, may not be. If you're sharp enough to ask the question then you're smart enough to handle either way. People are complicated. They have different sides and personalities. When one part talks sometimes the other disagrees. Who hasn't had the argument with themselves: Yes I will...No I won't...Yes I will...

no, as long as you know it is in your mind you're o.k.

the left brain and the right brain may sound different to you. Memories, and different ways of thinking can be from different times of your life.

Dealing with them has to do with the core of what they are about. Maybe getting a note pad, and listing simularities will help you sort it out.

The Holy Spirit can heal the soul into something simular of the innocents and purity of a new soul. And fill you with peace in hard times. Go to a good spirit filled church to learn this.

Well, you know what they say about people having beliefs different than their cultural upbringing to be mentally ill.
I think it's BS, in Greece when I was growing up we would write essays, which was a subject we were examined on to get into University. These essays were supposed to test judgment and critical thought as well as language, one of the phrases we used most often - and was droned into as by prep school teachers - was "the need for internal dialog" when talking about individual decisions as opposed to external dialog for group decisions. I've written it so many times as a positive thing, I do it, and I believe that anyone and especially Americans would be a lot better off if more of them did it instead of sticking to the "Just do it" mentality. I believe internal dialog to be the bases off critical thought - has anyone ever solved a difficult math/ physics problem without it?