If you did not purchase the optional Audit Defense product, you can phone TurboTax free Audit Support Center for help with an IRS letter.   At the page below click the blue "Get Help" button and follow the prompts to get the phone number.

https://support.turbotax.intuit.com/irs-notice/audit-support/

If you explain more about your situation in this user forum, you may get some suggestions here, too.  But this is a public forum, so don't post any personal info.

I believe i purchased the protection plan. I received a letter from the IRS requesting an additional payment of $2,369.22.

If you purchased audit defense before you filed, follow these instructions.
Contact the TaxResources Tax Audit Defense Customer Service Department at (877) 829-9695, by e-mailing intuit.audit.sales@taxaudit.com, or online at intuit.taxaudit.com/intuit.