Social Security & Medicare TAX

Did any XDJM met the same problem about tax deduction from payroll?--

Entered U.S. with F-2 visa, transfered to F-1(in U.S.) and now is working using OPT. Payroll consists that no tax exemption could be applied, including Social security, Medicare Tax and $5,000 Treaty Benefit because my initial visa is F-2.
So I have to pay for all the tax.

Thank you for your advice!!!