What to do if an internet provider harassed me for the bill

Hi Sir, I had paid for Hathway internet connection in July 2016. Documents were taken but I was not given any connection. I kept on calling for refunding the money. And every time I get a response different than the previous. I kept on receiving Hathway bills every month. I went to there office and complaint. They gave me a number. I called the concerned person. He said sent me the image of the receipt. I did so. Again no response from that person. I latter gave up. No one was giving any response. On 30th June 2018,I got a call from some person saying Hathway have filed a legal case because I did not pay a bill of 45000. As far as I know Hathway should refund me my amount and apologies for its fault. And now I got multiple calls says about the case against me. Hathway being the real culprit for my problems. I have been calling the nodal office for broadband. And some people keep on calling me and harassing me to pay.