The audio files have to be stored somewhere on the flash drive. I dont know where or what type of format they are in but I would think it would be possible to replace those files with professionally recorded files of the same format and/or file name. You may want to give Teleco a call, they should be able to give you a more defenite answer. As for the "memo" voiemail deletion, there may be an option to "delete on send" so that once it is sent to an email address, it is deleted out of the voicemail box. I know the Toshiba iES32/16 in-skin voicemails have this option, again, Teleco im sure can provide you with more defenite answers to these questions.