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