this is what TurboTax says
For Form 1099-R, enter the distribution codes shown in box 7 on the actual Form 1099-R unless you know that the codes are incorrect.
A distribution code must be entered. Enter the code or codes that accurately describe the transaction.
It is important that the correct distribution codes be entered. If the codes on the form are incorrect, you should try to obtain a form with the correct codes from the payer. Failing that, enter the codes that accurately describe the transaction.
there is no way to upload a copy of the doctor's letter. so to E-file you can't include it
if you want to file by mail you can include a copy of the doctor's letter and hope the IRS reads it. since the return is already late make sure you use a method whereby you know the IRS received it. if you get a notice from the IRS charging a penalty. dispute it. write a letter of explanation and include the doctor's letter. it could be a year or more before you hear from the IRS, if at all, because it's far behind in processing prior years' mailed returns. even e-filed it may take a while or you may never hear at all from them
the code should be 3 - disability
you can ask to talk to another manager at the bank if there is one. from their standpoint you are kind of late in asking. it may be their policy but I'm sure other banks don't have such a policy.
if they won't change it follow the above and I would ask the bank if they'll give you a letter stating that you presented a doctor's letter confirming your disability but it's their policy to code all pre 59-1/2 withdrawals as early distributions. they may refuse but if they do provide it and you get an IRS notice include it in your response.
