[CentOS] How do I change passwords / remove users for Samba?

I've got a bit of a problem with Samba. I just can't work out how to 
change passwords or remove users.
I've just got user security.. lines in smb.conf are:

         security = user
         passdb backend = tdbsam

I've removed the user using pdbedit, I've removed the unix user, 
smbpasswd says the user doesn't exist
yet I can still connect to the shares. I'm obviously just missing 
something here. Can anyone point me in the
right direction?

thanks