To customize the SMS message notification is possible using available filter “wpcsms_message” hook of the plugin.

Note: This “wpcsms_message” is only available with the SMS Add on 4.3.4+ version

The following sample code on how to customize SMS message.

function my_custom_sms_message( $message, $post_id, $find, $replace ){
    // Note: In this sample code will change the SMS massage when the shipment status is "Enroute"
    $status = get_post_meta( $post_id, 'wpcargo_status', true );
    if( $status === 'Enroute' ){
        // Note: Make sure that the metakey code exist in the system
        // In this sample code we used the sample metakey code
        // @ {wpcargo_tracking_number} - Shipment Number
        // @ {status} - Shipment Status
        // @ {wpcargo_shipper_name} - Shipper Name
        // @ {wpcargo_receiver_name} - Receiver Name
        $custom_message = "{wpcargo_tracking_number} - Status {status} from {wpcargo_shipper_name} to {wpcargo_receiver_name}";

        // Convert metakey code into actual shipment data
        $message = str_replace($find, $replace, $custom_message);
    }
    return $message;
}

add_filter('wpcsms_message', 'my_custom_sms_message', 10, 4 );