Is it permissible for a religious university student to answer male students' study-related inquiries on her personal phone?

It is permissible for a woman to teach foreign men under certain conditions: that there is no man available to teach the same subject, that the teaching is done from behind a حجاب (screen/barrier), that communication is limited to what is necessary, and that there is no fear of fitna (temptation/strife) from either side. If these conditions are not met, then teaching is not permissible.

Accordingly, it is permissible for students to call to inquire about the study if the teaching adheres to the Sharia-compliant conditions. This is supported by the fact that the Companions used to acquire knowledge from the Mothers of the Believers from behind a حجاب, and a woman's voice is not considered 'awrah (that which must be concealed). However, if the teaching is not regulated, it must be abandoned.