Thanks for the reply TE! You're right...I'm not a certified technician at all. Lol. I'm the System Admin here. We used to have our phone system managed by our Mitel phone provider, but unfortunately we had to cut support for budgetary reasons. So I've been charged with learning on the fly with no training. This forum has helped me a lot though.
As for my issue, I'd previously tried #1a, but that didn't change it. However, I tried your #2 suggestion and it worked perfectly. Thank you for that!
Regarding Message Notification Phone Destination...it's still pointing to the old extension, but I cannot change it. Any ideas?