I guess I am not understanding the problem... Are you saying basically you just need two auto attendants, one for 68897000 (Dept A) and one for 68897001 (example number, Dept B), and everything else to be routed to extensions (DID's)?
Let's back up a little...
What voicemail system, from the question I am guessing embedded VM? If so, you only get one auto attendant, but can use multi-level mailboxes for menu choices.
Absorbing digits and using system CDE speedcall is depreciated but still functional, but it would be much easier to control if you moved everything to the DID Routing Table form. This would also allow numbers to associated with users via the Users and Devices section (and also outbound caller ID if you wish).
Again, there are many ways to possible solve this, but I want to get a better understanding of the problem.