How do I fix the FICA withheld?

[JohnB5677]

It is unusual for FICA  (Social Security & Medicare) to be wrong.  The most common reason is that you worked multiple jobs, or changed jobs. 

Each employer calculates Social Security independently. If you earned more than $132,900 combined from BOX 3 if all your W-2 you will have overpaid.

This is not a problem.  It will be credited to you on your tax return on line 18 (d) of your Individual Tax Return.