Something went wrong when filing..The IRS took 1400 from my account after checking I received the third stimulus payment. How do I get it back?

The IRS changed your return, their records must show that you already received the $1,400.  You would have to contact the IRS about the change.  You should also receive a letter explaining the change & what you can do i f you don't agree with it.  The letter can take 3 to 6 weeks to arrive.

If you received the 3rd stimulus payment in 2021, you should have entered the information into your return for the Recovery Rebate Credit and you are not eligible for the credit.  If you claimed the credit on your return but did receive the stimulus payment, the IRS will adjust your refund.

To verify this, the IRS will send you a letter describing why they altered your return.