Professional ethics of lawyer in respect of opponent.

Dear members,

I would like to get clarity on the issue of professional ethics to be followed by lawyer with respect to opponent.

Background: I am heading a project office of an organization. Five years back we had taken Data Card (modem) for internet connectivity in our office. After using it for few months it was disconnected. Yesterday, a lady called me claiming to be an Advocate from Delhi High Court and telling that we have some bill amount due since 5 years. and they have sent notice and bill twice to our office but it returned back. (We have not received any such notice over these years and our office address remains the same). She insisted that we pay the amount the same day or she is going to register a case in court. When I checked with the company who gave provided data card using account number given by the Adv. Lady in Delhi, there seems some amount due (Rs. 4091). I called her back stating that allow us time to check our records and if any due amount remains we are ready to pay but only after we confirm with our accounts. We need to confirm because it was disconnected and company will clear all the dues before disconnecting and our organization also will not like to keep debts. But since then she has called couple of times and every time she used very rough tone of language and disconnecting without completing conversation. No civilized person will do like this nor will expect a learned person to act like this. Earlier it seemed official issue but now I feel ill treated.

Kindly advise.