"I'm sorry�" followed by the mailbox owner's name (as recorded by the owner or administrator), then "�is currently on the phone" and then the fixed system prompt, "Begin speaking after the tone, then hang-up when you are finished or press any key for further options."
Recording the message yourself doesn’t mean it can’t be done professionally. You can still get studio time with an experienced audio engineer. Studio time can cost $60-$100 per hour, which may or may not come with an engineer. If you need to hire one, their rates are usually $100-$300 an hour. Mind you, their feedback, professional experience, and editing capabilities are typically well worth the extra expense.

You can also erase any of your existing recordings associated with your voicemail box. To delete your name recording, unavailable greeting, or temporary greeting: Dial *98 on your OnSIP-registered phone. Enter your voicemail box number. Enter the PIN/password for your voicemail box. Press 0 for voicemail box options. Press 1 for unavailable greeting, 2 for your name, or 3 for temporary greeting. Press 2 to delete the existing recording on file.
In Australian English it’s pronounced with the vowel /a:/ like in ‘part’. Problems arise when people use the /ʌ/ vowel (like in ‘up’) instead of /æ/ or /a:/. If you do this is will sound like the worst swear word in English. Many non-native speakers often pronounce the vowel /æ/ more like /ʌ/ because they don’t have a vowel like /æ/ in their first language. Many speakers of European languages will do this (Spanish speakers and Italian speakers) and also speakers of Japanese and Korean. This problem with /æ/ also means that if you say the word ‘back’ in your voicemail greeting sample, you are likely to pronounce it more like ‘buck’. remember to pronounce word endings in English. Check you aren’t dropping any endings off or mispronouncing them.