My unusable iPhone

Two roads diverged in iPhone activation and I--I took the one less traveled by. And that has made all the difference. Instead of going for the standard postpaid plan, I opted for the prepaid one. I have signed up for a $29.99 per month Pick Your Plan with a $20 per month iPhone unlimited data plan. My account is fully provisioned on AT&Ts side and it shows as an iPhone compatible account. And yet, I cannot get past the "AT&T has determined that your current account cannot be used with the iPhone" screen. I'm told to call back tomorrow. The prepaid office is closed today. At least the iPhone looks pretty in its dock.