Hi mate, you can change the greetings by ftp ing into the 3300 ( via file zilla or similar programme). username and passwords are the same as the gui interface.
go to directory /vmail/c/vm/prompts/englishuk in here you will find files pday this is the main greeting and pnight this is the night greeting.
These files can then be transfered edited or renamed on the 3300 and a new file uploaded. Must be .vox
hope this helps