I have been non-resident alien in the last year 2018, and I have switched to a new employer in the last few months of last year.
Last month, I discovered that my new employer was collecting FICA (medicare and social security). When you are a non-resident alien, you are exempt from FICA.
I have asked them for refunding the over-collected taxes, they refused saying that I did not inform them of my filing status in 2018.
How to get the money back in this case? Does the IRS refund it?