Accused of false charges of personal loan

About 8 months back I received a few calls from a lady who was calling from a landline. She said that she was calling from an advocates office to inform me that a financial institution has lodged a legal complain in my name and in order to get more details I have to contact that advocate. I had saved that land line no. On my mobile. After a few months a man came to my house and said he was coming from a bank and that I had a credit card due. The bank he mentioned had closed operations about 8 years back and another bank had taken it up. This second bank had also closed soon and now a stronger bank had taken up all the operations. He said he was coming from the present bank. I told him that I did have a credit card of the first bank and my husband had used my credit card and after making some payments, had stopped paying. This was about 10 years back. My husband has eventually abandoned me and my only son a few years back. I told him that there was a small amount due but I have lost all the documents regarding the credit card and now I am not in a position to pay as I dont have any financial support. I am barely managing to bring up my son and survive with the help of a temporary job. He then requested to use my mobile phone and called his office. After that he said that he will try to help me by reducing the due amount and allow me to pay in installments. After he left, I checked my phone and found that he had called the same number which I had saved as that advocate's number from where that lady had called. Then I felt that something was wrong and stopped taking their calls. The man came to my house many times after that but I was not there. After 2 months, he came with a lady and when my elderly mother told them that I was not at home, the lady spoke harshly to her and said that I have taken money from the bank and I have to give it back. My mother told her that they wuld have to talk to me and not her and the lady told her that my mother has to listen to her as I am not attending their calls. She even threatened my mother that it would be bad for us if stones were thrown at our house. I called up the man after one day and told him this is not the way to talk to people according to the code of conduct of RBI. He said that she was his boss and he wanted to help me. He said if I pay him 500 rupees a month till i could settle with the bank then the amount I pay will be adjusted later during settlement. I said I am not in a position to pay any money. That lady called me after a few days and said she would settle the amount for 7500 rupees. The total due mentioned in statement provided by them was around 35000 rupees. The satement was of 2012 and of the 2nd bank. I told the lady that she had no right to talk to my mother like that and she should apologise. She said she did not say anything bad and she also had seniors to report to. I disconnected the phone. Next day the man called and said that the woman was from a DSA appointed by the bank and he was directly from the bank. He told me not to pay anything to the DSA and no one could do anything to me regarding credit card dues. He asked for 200 rupees for his daughter's medicine. I said I dont have money. He called me after a month again today and said that there was a personal loan in my name also from the same bank which had closed operations 8 years back and where I had this credit card due. I said I didnt have any personal loan from that bank. He said he could provide me documents. Please suggest what should I do?