Ron,
You say, "Current numbering in the 200 - 300 range.... with the DID's ....in the 3340-3389 range.
OK, that's a good place to start.
However, we need to know the EXACT RANGE of the CURRENT EXTENSIONS.
Are they 200, 201, 202, up to 3xx or 240, 241, 242, or WHAT?
You can (With Legend/Magix PRI)take a D-I-D (PRI, sending 4 digits) of say 3340 and point it to 200, and then take 3341, and point it to 201, and, and, and.... but that is not what Mister Spock (of Star Trek fame) would say is logical.
It doesn't have to be logical, but it makes more sense to the end users and their clients if it is.
SO, how do you want this to come to pass.
Should we change extension 200 to 340, or should we point 340 to extension 200? BUT DO YOU REALLY WANT TO DO THAT????
Again, not much sense can be made of this for those of us who like to see MATCHING NUMBERS ... (My D-I-D is 3340, but my Extension is 200, DUH???)
How does your client want this to work (LOGICAL, OR "DON'T CARE) - AND/OR - Can you negotiate a different set of D-I-D numbers from the vendor which will match your current dial plan? (That would be ideal, of course.)
This issue, I'm afraid, will not be solved in only one or two posts.......
ALSO, How will this impact things such as their BUSINESS CARDS? That is something to consider, for sure....
Please consider the points raised, and let us know......