After you file

@Dmcconnell863 No you cannot change banking information after you file your tax return.   Changing your banking information in TurboTax does not transmit it to the IRS.   If your Form 1040 showed the credit on line 30 then it was a part of your tax refund and was added to the refund shown on line 35a.   If the IRS reduced your refund they will send you a letter telling you why.    

And... $1600?   The first stimulus check was for $1200 for adults and spouses and $500 for dependent children under the age of 17.   The second stimulus check was $600 per each spouse and each dependent child under 17.   So your credit amount must have been reduced by your income or the amount you had already received.

The amounts for the first and second EIP payments and eligibility per the IRS:

A1. Generally, if you are a U.S. citizen or U.S. resident alien, you will receive an Economic Impact Payment of $1,200  ($2,400  for a joint return) if you (and your spouse if filing a joint return)  are not a dependent of another taxpayer and have a Social Security number valid for employment and your adjusted gross income (AGI) does not exceed:

• $150,000  if married and filing a joint return
• $112,500 if filing as  head of household or
• $75,000  for eligible individuals using any other filing status
  Your payment will be reduced by 5% of  the amount by which your AGI exceeds the applicable threshold above.

You are not eligible for a payment if any of the following apply to you:

• You may be claimed as a dependent on another taxpayer’s return (for example, a child or student who may be claimed on a parent’s return or a dependent parent who may be claimed on an adult child’s return).
• You do not have a Social Security number that is valid for employment.
• You are a nonresident alien.
  The following are also not eligible: a deceased individual or an estate or trust.