You can ask your
employer to read the IRS publication about FICA Taxes (https://www.irs.gov/pub/irs-pdf/p15.pdf). If they continue deduct taxes, then you can
request refund of FICA Taxes withheld from your paycheck back from IRS.
You can file IRS Form
843, Claim for Refund and Request for Abatement. Follow the directions
in the link below.
https://www.irs.gov/individuals/international-taxpayers/social-security-tax-medicare-tax-and-self-em...
See also for your
reference:
http://www.happyschools.com/opt-exempt-fica-taxes/