I've had a similar experience...
I originally ordered my base model rMBP a couple of days after the WWDC. A day or so later it came to light that it isn't user upgradeable, so you can't add more ram like in previous MBP's. So I decided I would change my order to upgrade it to 16GB rather than 12 months down the line regret not doing it.
So I tried to call the rep I had initially dealt with over the phone, but she wasn't available. So spoke to someone else, a very nice American lady, my original rep was Irish

After trying to explain what I wanted to do she said they can't amend the order and I'd have to cancel and reorder. She advised I speak with my original rep to see what she could do. She finished the converation with something along the lines of 'let me know once you've got it sorted and I'll see what I can do to compensate you for the trouble'.
I kinda thought nothing of it as it wasn't really their fault, just me Mr Awkward customer changing my mind
Now after reading this thread I've emailed the American rep asking her, in a round about fashion, if there is anything she can do due to having to wait an another week on top of my original delivery date.
Laid it on thick though, as original order was due before I went on holiday. New order now likely to land while on holiday and possibly even after my birthday!
Lets see what happens...
(A free MBA would be nice

)