How to file an appeal to changes made

[LXXVII]

IRS made a change to a previous return (Received notice CP24). I responded, disagreeing with the change, and then followed up multiple times in order to resolve. I've gotten nowhere, as every rep I've spoken with can't explain or justify the change. I assume filing some type of more formal appeal is the next step. What is the process?

[Vanessa A]

You can try contacting the Taxpayer advocate service. They may be able to help. 

[LXXVII]

Publication 5, Your Appeal Rights and How To Prepare a Protest If You Disagree

https://www.irs.gov/pub/irs-pdf/p5.pdf