After you file

My husband died on February 1, 2021. When our stimulus arrived, I called Senator Lindsey Graham's office to ask if he was eligible for this stimulus. They told me he was not eligible and I should return the $1400. to the IRS in Memphis, TN. I wrote a check and sent it along with a letter giving his Social Security number and his date of death. They cashed my check. When he got a letter from the IRS #6475 stating that he had received this money I called the IRS and was told that indeed he was eligible. I have been trying to get a refund. Yesterday I got a letter stating that I needed to file a 1040-X Amended tax return. I have printed this form but I don't see a place for Recovery Rebate Credit, which is where the IRS to place the $1400. Help