It's not clear what happened here. The IRS doesn't send a refund for a W-2. It sends a refund for the amount on line 35a of your Form 1040 tax return. Did the IRS change your tax return after you filed it? If so, they would have sent you a notice explaining the change, and the notice would have given you an opportunity to object to the change. Did you get such a notice? If so, when did you get it? Did you respond to the notice? When did you file your 2021 tax return?
What is the exact amount on Form 1040 line 35a of the 2021 tax return that you filed? What is the exact amount that the IRS changed it to? What is the exact amount of the refund that you received?