Samba Permissions after changing Host name

We install our Severs here with the same host name. Samba works fine. When we change the host name, for our customers, Samba tells me, we don’t have the right permissions. When we change the host back tot he insalled name, it works. We change the name in „/etc/hosts“, Setting-Details and with command hostname. We are new with Red Hat and our not sure where else we need to change it. Can anybody help?