Incorrect First Covid Payment

When I filed our return in 2019, Our adjust gross income was about $152,000.  We received our first covid-19 payment of $2,350.  I subsequently received and updated 1099-R from our brokerage house and it ended up lowering our AGI to $148,000.  That means that we should have received the entire $2,400.  I was told that I would be able to get the $50 as a credit on my 2020 taxes.  I just ran did our 2020 return and this years AGI is over $150,000 so that the payment in 2020 was correct.  I think that is wrong but I don't know how to get the money we should have been paid.  Any suggestions?