The task is basic IVR, pick up the phone immediately, greeting: "welcome, please press 4 to reach person A, please press 6 to reach person B or press 0 or stay on the line to reach general mailbox". dialing out no restrictions on dial pattern.
if you doing it on a regular basis you should be able to have ready to use recipes, aren't you? if you have or can suggest a better one please do.
Do you have phones? and will you want them set up for remote provisioning or do you just want me to configure the extensions and let you provision them?
I have ATA, no other phones needed. I can configure ATA myself, connecting to an extension