To whom shall we write to seek clarification

Hello Everyone,

My company has given a portion of its building on rent to an Educational Institution. As per our knowledge Service Tax is applicable on this & so we are charging the same on invoice. But the Institute is arguing with us that it is not applicable in their case. So, we wish to seek clarification on this issue from the Department. Kindly, tell me, to whom we should write to seek clarification on this issue. Our premises are located in Gurgaon, Haryana.

Thanks in advance.