System recording files

I’d like to customise the following system messages. I went to /var/lib/astrerisk/sounds/en/ location and there are soo many recordings in there. Does anyone happen to know the location/filename’s for the following messages only?

Voicemail instructions:
After the beep, please record your message. When done hang-up or press the pound key

After leaving a voicemail:
Thank you, Goodbye
There was an error

When outbound call requires a pin:
Please enter password followed by pound key
incorrect password, Please enter password followed by pound key