Stuttering is what it is.  It reacts on fear.  My environment is the least perfect. I do sales talking to strangers but humans are adaptable.  First there was intense fear with the cold knocks, could barely introduce myself, literally blocked they looked away and moved on and it decides to let go, then over time got less and less scary and stuttered less and less over it.  It is what it is.  The more you resist and fear it the more the body reacts as if your life is on the line for God knows what reason.  Something just isn't right but the only surefire cure I experienced was putting myself out there anyway until sales became as common as talking with the wind.  I'm at an emergency job now and talked with the client all morning comfortably, at the beginning it was nothing like this.  Sometimes the only way out of the storm is to go through it.