@HERBMOM Yes they show they sent you 4200. The letter you got was only for one of you. They sent each spouse a letter for half. So 2100 x 2 = 4200. Did you claim a dependent on your 2020 or 2019 return? If you got a Stimulus payment for a dependent you aren't claiming for 2021 you don't have to pay it back.
Double check your bank statements again and Check your IRS account (both accounts if married)
Your Online Account | Internal Revenue Service
If the IRS thinks they sent it to you but you didn't get it request a trace for a missing third Stimulus payment
https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-p...
