samba - Sep 2002 - user can't change password from woskstation

Hi,
using samba as PDC has already successful been access from WinNT client, but 
clients can't change their password from NT. 
Any posibility to do that? or I invite them to access my samba server one by 
one?
here is my smb.conf
[global]
workgroup = ACACOM
os level = 64
security = user
encript password = yes
preferred master = yes
local master = yes
domain logons = yes

Thank in advanced

Indra