Okay, so i managed to get the surfplot to show the timestep using the following code:
    % code
    %# delete the previous annotation
    delete(findall(gcf,'tag','timestep'))
    %# create new annotation
    annotation('textbox',...
    [0.72 0.68 0.18 0.16],...
    'String',{'time',i*dt 'sec',},...
    'FitBoxToText','on',...
    'tag' , 'timestep');
  end


