Please this answer below --> https://ttlc.intuit.com/questions/4668034-i-am-a-student-on-an-f1-visa-my-income-was-through-an-inte...
You first have to try and get the refund from the employer whom withheld FICA in error before going to the IRS. Generally it should be one claim covering all the employers ( if one or more refuse to give you the refund ).
When did you enter the country on F-1 ?
