Yup, it looks like if you're a Premier customer, you're going to have to call them in the morning. (866) 499-8008. I love how they treat their "Premier" customers. :-/
This is what they say about the $100 discount:
$100 off MOTOROLA ATRIX(TM) 4G after instant rebate with qualified voice and data plan. Additional restrictions apply.
Requires a qualified 1-or 2-year service agreement for Corporate Responsibility Users (CRU) and requires a qualified 2-year service agreement for Individual Responsibility Users (IRU). Also requires activation on an AT&T voice plan with a Monthly Service Charge (MSC) of $39.99 or higher plus (i) for IRU customers a DataPlus Personal plan or other eligible data plan with MSC of $15 or higher; (ii) for CRU customers a DataPro Personal Plan or other eligible data plan with MSC of $25 or higher; or (iii) DataPro Enterprise plan or other eligible data plan with MSC of $40 or higher; or (iv) Smartphone International plan of $64.99/mo. or higher. On DataPro/DataPlus plans for Smartphone and iPhone, if you exceed your initial data allowance, you will automatically be charged an additional $10 for each additional 1GB provided on DataPro or an additional $15 for each additional 200MB provided on DataPlus. All data allowances, including overages, must be used in the billing period in which the allowance is provided. Access to corporate email, company intranet sites and business applications requires a DataPro Enterprise Plan. Offer cannot be combined with any other equipment promotion, discount or other offer. Subject to availability limitations. Sales tax calculated based on price of unactivated equipment. Limited time offer. Flat Rate plans, FamilyTalk and Add-a-Line are eligible. Offer runs until Monday, April 04, 2011 11:59pm EST.
I don't see anything about the Data Unlimited plan, but it does say flat rate plans are eligible.