documentclass{report}

makeatletter
newcommand{unchapter}[1]{%
  begingroup
  let@makechapterhead@gobble % make @makechapterhead do nothing
  chapter{#1}
  endgroup
}
makeatother

pagestyle{headings}

begin{document}
tableofcontents

chapter{Regular}

Text

unchapter{No chapter head}

Textnewpage
text: check the heading

chapter{This is regular again}

end{document}