F-1身份要付social security tax 吗？

收到social security来信说“our records show that you have been employed in work in which you did not pay social security taxes”.可我除了学校TA的钱， 没有别的收入。而学校都是tax withhold, federal and state. 难道突然去年新规定，说是学生要自己交social security tax? 我该argue 吗？