Nextra Broadband - Refund of security of broadband

I was using the nextra broadband service . Due to poor service provided by them and high charge . I stop using its service . I called so many time on call centre to stop my services and refund my amount . But nothing happens. In July I called on call centre to stop service . However the call center people fool me every time and misguide me . They are not giving the proper information about the refund . They are delaying the process. Even the router has not been collected and as far as security is concerned .... Nothing happens. I also put email to their grivenace redressal site but I don't get the response from their site .Kindly help me to get my refundable money .