Axis bank - Call center harrasment

I have pending credit card payments with Axis Bank and due to few unforseen situations I was unable to pay regular dues. They started calling me and I was responding to their calls and explaining the situation. One day a guy from a call center called and was rude and using un parliamentary, abusive/vulgar language.
I have given a written complaint in axis Hyderabad but still I have received the calls and one of them repeated the same thing. The major issue is they called my sister in law repeatedly regarding my dues where she doesn't have any connection to my bill payments, I have never provided her number in bank, how did they get her number. Are they accessing my contacts is what my question is,my father was also responding to the bank calls. Still they haven't stopped calling her.