Netplus Broadband - Internet

I have requested for disconnecting my netplus broadband about a month ago. They have sent me the bill for using the service. When i started new connection they have told me that *** rs is for security and when you disconnect the service your security will be adjusted in the bill. but they sent me the full bill. it's been a month since i have been calling them to collect the router and the bill from my home where they put up the connection. Nobody has responded. Also, they said if the bill is not paid before certain date there will be an extra charge.