The MONTEL.INI and DEFAULTS.INI files are the same file. The DEFAULTS.INI file is typically a copy of a MONTEL.INI file from a preferred set up on a client computer. While it is possible to edit and maintaining manually, the recommend way, is simply to copy an existing (and correct) MONTEL.INI file. This way if settings change or a re added the DEFAULTS.INI file will be up to date.
You can however edit the MONTEL.INI file or DEFAULTS.INI file directly. It follows the standard INI file format, and you should edit it with NOTEPAD.EXE.