Totally agree with the advice to try mindfulness. Don't try to suppress the voices. The more you resist them the stronger they get.
Read the book or watch the videos by John Kabát zinn and read mindfulness in general. It won't be easy, it'll take practice, but after some time, you'll be able to notice the voices without them causing too much distress.

Of course, if your problems are severe, you always want to follow your doctors advice and use medication they prescribe