Search result shows usernames instead of displaynames

Hi all

I'm using Openfire 3.10.2 + Spark 2.7.1.686 + LDAP + SSO on a Windows 2003 Domain Level (Openfire Server Windows 2008 R2, Spark client W7 Pro). I've tried and I'm using auto populate AD users using some groups, but I don't want to add all users. So, I want to use the 'Search contact' option but at search results Spark is showing username (samccountname@xmpp_domain) instead of Displayname.

Any idea for changing this? My users doesn't know other users' samaccount so they cannot find them

Thanks in advanced