It sounds like this may be a known scam that the IRS recently issued an alert about. Please review the information in this IRS link carefully then call the IRS at at 800-829-1040 to ensure it wasn't a recalculation. If it is not a recalculation, follow the procedures listed in this link (void the check, etc): https://www.irs.gov/newsroom/scam-alert-irs-urges-taxpayers-to-watch-out-for-erroneous-refunds-bewar...
