After asking around in the Getting Started forum, the general consensus from a few long time Public users was that the automated system instructions played to incoming callers after hearing your personalized greeting can't be disabled.
These prompts sound similar to "press 1 to leave a call back number, press 2 to re-record your message, or hang up and your message will be sent" or words to that effect.
I find them redudant and unnecessary. I hope that Public can alow users more options in the voicemail box setup so that those instructional prompts could be turned off.