The IRS will adjust your refund if you claimed the Recovery Rebate Credit but didn’t qualify or overestimated the amount you should have received. If a correction is needed, the IRS will calculate the correct amount of the 2021 Recovery Rebate Credit, make the correction to the tax return, and continue processing it. There's no need, at this point, to amend your return.
There may be a slight delay in processing the return, and the IRS will send a notice explaining any change made. If this happened to you, you should get a letter from the IRS explaining the reason why your refund was impacted 2–4 weeks after it was issued.
If you disagree with their decision, you should review the notice and the Recovery Rebate Credit questions and answers before contacting the IRS. They provide additional information to explain what errors may have occurred and what information to have available when contacting the IRS. Once you've reviewed the letter, contact the IRS with the number provided on the letter. Please be aware that they're currently experiencing extremely long wait times due to COVID-related staffing shortages.
Check out this IRS release for more information about the Recovery Rebate Credit information letters and what they mean.