If you have an OEM license, then it's valid for the original machine only. If you have a retail license, then it's transferrable to any future machine. During the phone call, if you make it clear you're retiring an old machine and commissioning a new machine, you should have no problem during the phone call. The staff also seem to exhibit a certain flexibility based on your assertiveness: "this is what I paid for, therefore this is what I expect" seems to work quite well.