Contact the payer to obtain a corrected Form 1099-R. If they refuse to provide a correction follow the instructions in IRA Tax Topic #154: https://www.irs.gov/taxtopics/tc154
Finally, if you can't get a corrected form from the payer, file a substitute Form 1099-R (Form 4852) by marking the "I need to prepare a substitute From 1099-R" box on the Tell Us Which 1099-R You Have page and make your changes.
