You are going to have to return the item and hope they have what you want in stock. Since you want the 6 plus, I doubt you will find what you are looking for. Might have to wait for shipping or try following what I did on this thread, after you've already returned your phone of course.
I'm in the same boat. Think I'll head in this Saturday and try my luck. I should have thought it through and coughed up the extra $100 up front but the price was already pretty steep to me since I got one for my wife as well (she's fine with her 16gb 6)
I have been trying this. I returned my 16gb + and have resorted to waiting the 3-4 weeks on Apple.com. I'll occasionally check the online tracker, but there are literally no phones available in my area. It's becoming an exercise in patience.