The IRS generally won't take tax law violatoin referrals over the phone. The best way to report this is Form-3949-A.
See: https://www.irs.gov/individuals/how-do-you-report-suspected-tax-fraud-activity
From the details you provided he would have had to forge your name on the return and then cashed your refund check.
Answered on Mar 18th, 2021 at 10:52 PM