Answered question
Is it possible to change fizz's default voicemail greeting with another pre recorded message?
Sorry, I dont think so.
Other option , I would suggest, you choose to change it for yours.
Other answers
Michel is right, the other alternative option is to use a computer TTS program to record your voicemail if you’re not comfortable recording it yourself. Microsoft has a built in one in windows.
there is no other prerecorded message, you can record your own or ask somebody to record it for you :) but it is usually better to have your own voice, so people do not confuse.
You can record your own.