Abstract: A method includes receiving a call setup signaling message at a subject line messaging application server. The call setup signaling message includes a subject header. The subject header includes a message identifier that corresponds to a subject line message selected by a caller device. The method includes replacing the message identifier with the subject line message to form a modified call setup signaling message when a removal determination indicates that the subject header should remain. The method also includes sending the modified call setup signaling message to a called party device via a server.

Abstract: An example apparatus includes a memory and a call session controller. The memory is to store a first public user identifier in association with a first nomadic service designator and a first operating mode designator, and to store a second public user identifier in association with a second nomadic service designator and a second operating mode designator. The call session controller is to determine whether a first call using the first public user identifier is eligible to be established based on the first nomadic service designator and the first operating mode designator, and determine whether a second call using the second public user identifier is eligible to be established based on the second nomadic service designator and based on the second operating mode designator.