The stratagy voicemail has been a few years since I touched it. If you can get the manual(buy it from your vendor), and the passwords. The auto attendants from memory are accessed through a mailbox, Memory says mailbox 999 is the admin MB , mailbox 997 is usualy a default mailbox that can be copied to create a new mailbox(if it was set up as a default box with the correct parameters in initial install). Main auto attendant greetings are in MB 990 the hello box, 991 the greeting box. Always listen to a greeting by calling in first, then access the auto attendabt MB, and listen to it to verify you have the right one before re-recording.
I always created a text file that had a single number 1 in it, and copied that file into 990 as the greeting sound file, which made the VM skip to 991. Then record everything there for the AA greeting. It made it easier for the users to admin it then, and I do not think 990 would accept dtmf, so you had to wait to dial your ext until it played the 990 greeting then proceeded to MB 991.
Once again, this is from memory, and if I was sitting in front of one, I know I could do it all, but my memory is not perfect. I do recall, once it was set up, I could call in to do most any changes I needed to, that were typical admin changes.
I would call a local vendor and get some admin training, it would be worth it. You should be able to do anything you should even be attempting through a phone, and logging in with a password to the dtmf admin interface. If you need the software to do something, have a tech do it. At least, have a tech set up the software if you want to use the software to admin.
You do not always get what you pay for, but you never get what you do not pay for.