As TaxPro+40 suggested, it's a good idea to verify the letter is real by phoning the IRS at the number he provided rather than the one on the letter. There have been some scams involving letters, but it's not as common as fake IRS phone calls.
Since you purchased Audit Defense, they will help you with understanding an IRS Letter and how to respond, etc.
You can go to intuit.taxaudit.com and select Member Login (upper-right corner) or call (877) 829-9695 toll-free. Don't pay again there, since you are considered a "Member." If it was me, I'd probably call first and tell them what you received.
