Lets see if I can explain this....
I have 18 BB's on an AT&T (Cingular) account. All are on a BES and I have complete control over the BES server as well as the AT&T account.
My phone is not eligible for an upgrade, but some others on my account are.
The AT&T rep told me that I could upgrade another phone and just swap the SIMS with my phone. However, they said that they would change the IEMI number in their computer system on the old phone. So, techinically, the old phones SIM would have this new IEMI number associated with it.
So, if I upgraded a sales guy phone and kept the phone for myself, would I have to reset up his old phone on the BES?
thanks.

Wirelessly posted (BlackBerry8700/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/100)

I don't think you would! But you could always call back and have customer service swap the IMEIs back. Actually explain to rep what you are doing they CAN do the upgrade then swap the imeis around before you even leave the store

yes, I would agree with you in principal. The rep should be able to do all of this for me. However, sometimes the reps do not have driveways that go all the way to the street

EZrunner is correct. Take a few minutes to find a CSR who can speak with some amount of authority on the process.

Explain in detail why you are swapping the IMEI data for the phones and why you would like it swapped back at the end of the process.

This is a very easy thing to do for a properly trained wireless CSR. Certainly easier than sorting out customers "overbilling", whether actual or perceived =)

As long as you ensure you are speaking to a competent individual, this should go as smooth as silk.