Excitel - Internet service issue

I have Excitel as my internet service provider and suffering from connectivity issues for the last month. In the last one only get * days on the internet. Every time when I call customer care they say they are working on the problem but it been more than ** days. Nobody gives any email or phone of higher officials and consumer is suffering. I told them to terminate the service and refund the money but they say its prepaid service money cannot be refunded. I want to know they are not providing service nor they are refunding the money as a consumer what should I do. I purchased internet because I had work to do but now not able to do because of connectivity and can't change service provider because of * months advance payment has been made and ISP is not giving service and neither the refund. Its caused a lot of inconveniences. This issue is in west Delhi Tagore garden guru Gobind Singh Kunj.