What are you wanting/needing? You'll need to explain your issue, so folks will know if they can help you in this forum. Did you get an IRS letter/notice? If so, what type (see second FAQ below)?
Why do you mention "audit defense?" Did you purchase that product and want to know how to contact that company? Or are you wanting to know how to purchase it after filing? Or are you wanting to know about TurboTax free Audit Support Center?
FAQ: TurboTax Audit Support Center
https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-audit/turbotax-audit-support/L6AcMoNFD_US_en_US
FAQ: I got a letter or notice from the IRS
https://ttlc.intuit.com/turbotax-support/en-us/help-article/internal-revenue-service/got-letter-notice-irs/L2JDxmDTo_US_en_US