pasted directly from the change password page
"Your password must contain a minimum of 8 and a maximum of 16 characters with at least one uppercase letter or a number. You can use the letters: A-Z, a-z; digits: 0-9; symbols: . (full-stop), _ (underscore) and - (hyphen) in your password."
If your password meets those requirements already there would be no need to change it.
If it is a telstra modem and your internet service uses the same email address, provided that it is online when you change the password, it will get sent automatically to the modem for you