Fraud in internet

I am facing internet issue from last 5 months, I called Airtel customer care on every alternative day. But they don’t have any response for this issue, they suggested me to change my sim and I do so, but the problem remains same. But when it comes to bill payment they want it on time if not paid then fine will be charged, but when it comes for customers problem there is no response. So I request you to take some action on this bogus company