Unexpected CP21B Notice Showing $13,022 Refund from 2023 Taxes - I Didn't Request These Changes

I filed my taxes electronically on 2/1 and still no refund, but now I just received a CP21B notice dated December 24, 2024 for my 2023 tax return. The WMR tool has just been showing "being processed" for weeks and my transcript had no updates until this notice arrived. The notice says: Department of the Treasury Internal Revenue Service Austin, TX 73301-0025 Notice CP21B Tax Year 2023 Notice date December 24, 2024 Changes to your 2023 Form 1040 Refund due: $13,022.00 They made changes I requested to my 2023 Form 1040 to adjust my: - income from wages, salaries, tips, etc. - self-employment tax Summary: Account balance before this change Decrease in tax Refund due: $13,022.00 The notice says if I haven't already received the refund, I should receive a refund check within 2-3 weeks as long as I don't owe other tax or debts they're required to collect. It mentions the refund amount may include interest, and any interest received is considered taxable income during the year I receive it. I'm confused because I didn't request any changes to my return. Starting to get worried since I usually get my refund within 21 days of filing, and now this notice mentions changes I didn't ask for. What's going on? Anyone else experiencing delays or unexpected notices this year? What's considered normal these days? Should I call the 800-829-8374 number on the notice even though I didn't request these changes?