How can I change or get dynamic IP address?

I am using USB modem for internet connection. I have heard that, it is possible to change IP address. I have also heard that by using ';Network Protocol'; some one is changing their IP address. Actually I am a freelancer so, i need this for my work. Various DNS related websites are helping, I have also heard. If anybody can please help me.How can I change or get dynamic IP address?
Most users receive a dynamic IP address from their Internet Service Provider (ISP). Only a handful of users get a static IP address without asking for it. Static IP addresses are normally only used by companies, for use with their web and mail servers for example. Dynamic IP addresses do not mean that you get a different IP address everytime that you turn on your modem. Dynamic IP addresses have a so-called lease time, which is the time that the dynamic IP address is assigned to you. This lease time might be one hour, one day, one week, two weeks, one month, et cetera. You state that you would need to have a dynamic IP address and that you would need to be able to change it. To find out if you have a dynamic IP address, either simply ask your ISP if you have a dynamic IP address, or keep an eye on http://www.whatismyip.org during a week or so to see if your IP address has changed. Turn off your modem to see if this hurries up the changing of your IP address, as sometimes turning it off and on again refreshes the IP address assigned to your modem. As for needing to change it, why would you want to change your IP address? First of all, you would not be able to choose a new IP address. Your new IP address will simply be a different IP address taken from the DHCP pool from your ISP. Second of all, a different IP address does nothing for you. It does not hide your identity in case you might think that, as your ISP simply keeps track of you no matter which IP address you have. Every IP address which you have had is logged and will trace back to you, even if you have received a new IP address yesterday, what you have done the week before can still be traced back to you based on your old IP address. DNS is provided by your ISP. You simply use the DNS from your ISP. If you wish to have a DNS entry of your own, you would be better of with a static IP address instead of a dynamic IP address. DNS is only used if you would run a service on your own network, such as a web or mail server for example. You seem to have heard a lot of stories, but none of them are true or they do not apply to you. Have a look via Google to learn what an IP address is, TCP/IP, DHCP, DNS, et cetera, so that you know what you are on about. If you have anymore questions, feel free to contact me.How can I change or get dynamic IP address?
you can actually set up a static ip on your computer,which means your computer will pull the same ip from your isp/modem...go to your network connections,right click and go to properties,find TCP/IP settings there you can make all the changes...