Should I amend married to single?

I got married in December of 2019. We are both Ca residents. I filed my taxes as married filing jointly. I did not enter my 1095a (I had Medicare for 7 months and never used it) and I got my own health insurance from my work. I thought nothing of it. I received a letter from the IRS requesting form 8962 and my 1095-a. I attempted to fill it out, and boy was it hard. I then went on turbo tax to see if if they could do it for me, but there is no way to differentiate that we had a combined income for only 1 month. I would have to pay 2000 dollars. When on the 8962 form, it’s possible to adjust for marriage time (somewhat). I then made an amendment to see what I would owe if I filed single. And did the 1095a and I would only owe 800 dollars. What should I do? Thanks for your thoughts. As I understand it, the IRS would not know that we are married or not. As we haven’t changed our names.