itemize, removing natural indent

Any customization of a list environment, such as itemize, enumerate, etc, is most elegantly handled by the enumitem package.

You can use leftmargin=* locally,

\begin{itemize}[leftmargin=*]
  \item one 
  \item two
  \item three
\end{itemize}

or else you use

\setlist[itemize]{leftmargin=*}

in your preamble to make the change global.

\documentclass{article}
\usepackage[showframe=true]{geometry}
\usepackage{enumitem}

\begin{document}

\begin{itemize}
  \item one 
  \item two
  \item three
\end{itemize}

\begin{itemize}[leftmargin=*]
  \item one 
  \item two
  \item three
\end{itemize}
\end{document}