How do I get my dhcp address to change?

[Michael Michalchik]

We are attached to the internet through a cable modem. It seems like
someone germany keeps port scanning us. We'd like to try switching our
ip adresss to something different to hide form whomever this is. We
shut down our server for about half an hour, but our ISP kindly
restored our original IP address. Is there a way that we can for our
IP to change? Is there some sort of request we cxan send or trick we
can do by temporarily turning off DHCP and sending an invalid request
for a fixed IP?