Oracle Datafiles shows same name

How to change the datafile name for the below datafiles and how to increase the system datafile in Windows environment? I guess I have created the datafiles wrongly and these are OMF. Please help in resolving this issue.

SQL> SELECT SUBSTR (df.NAME, 1, 40) file_name,dfs.tablespace_name, df.bytes / 1024 / 1024 allocated_mb,

  2  ((df.bytes / 1024 / 1024) -  NVL (SUM (dfs.bytes) / 1024 / 1024, 0)) used_mb,

  3  NVL (SUM (dfs.bytes) / 1024 / 1024, 0) free_space_mb

  4  FROM v$datafile df, dba_free_space dfs

  5  WHERE df.file# = dfs.file_id(+)

  6  GROUP BY dfs.file_id, df.NAME, df.file#, df.bytes,dfs.tablespace_name

  7  ORDER BY file_name;