How to change or create new service name in Oracle Database

1-) Modify service_names parameter and add new service name:
SQL> alter system set service_names='{new_service_name}' scope=both;

2-) Add following SID description to listener configuration (listener.ora)

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = IP)(PORT = PORT))
    )
)
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = {new_service_name})
      (SID_NAME = {oracle_sid})
      (ORACLE_HOME = {oracle_home})
    )
  )

ADR_BASE_LISTENER = {oracle_base}

3-) Restart listener.
Now you may connect to database using following tnsnames.ora configuration:
{tnsname} = (DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(Host = {host_name})(Port = {port}))
(CONNECT_DATA =(SERVICE_NAME = {new_service_name})))