You wont be able to hav static ip for free, partly because IPs are purchased for a price when ISP registered as host from the institution that maintains all classes of IP addy. For example, internic. So, im really curious who would be so generous to purchase that static ip and give you for free.
However, im aware that if you configure your router that is linked to the cable, you could program that router of yours to always attempt to request for a particular ip address (provided no one is using it). Otherwise, switch to another ISP that uses a relative more static IP addy.