Harassment over phone from recovery agents how to proceed legally

Case: Few guys are consistently calling my wife in his office and on her personal number which they got through from some social media. They have called at my office as well. They have threaten to kidnap her as well. Issue was related to her fathers loan from barclay bank which was supposed to be settled between bank and him. As my wife and me we work in MNC and appeared to be easy target for them they are reached to any level and abusing us everyday even at our work place. we have started recording their calls and in process to file FIR to police. My query is what are we liable to pay loan on somebody's else behalf by LAW relative and what we can do to teach these people lesson for harassing us and several others like us.?