I can't see the IRS letter or your tax return, but based on what you have said I would suggest that you send them a copy of the 1098-T, a copy of the student account statement, and proof of any payments that you made, such as copies of canceled checks. Follow the instructions in the letter for how to respond, and be sure to respond by the deadline in the letter.
I would also suggest calling the TurboTax Audit Support Center before you respond to the letter. They might have more helpful information.
Send your response to the IRS by certified mail with a return receipt, so that you get tracking and confirmation that they received it. Send only photocopies of any documents, not the original documents.
