client cant call through my asterisk server

why client cant call through my asterisk server??
i set up asterisk in LAN, i can call to a client from the server...but client cant call up through the asterisk...
i had disable the firewall and SELinux...so what is the problem???
Help, pls....
i set up asterisk in LAN, i can call to a client from the server...but client cant call up through the asterisk...
i had disable the firewall and SELinux...so what is the problem???
Help, pls....