Sim card for iphone 3G so i can use it on a cheaper server?

My Verison contract expires in March. Have unlimited calls, texts etc. Costs $138 mo. Wanna use my Iphone 3G and go to a cheaper server with rates of say $60. Can I use my Iphone 3G on another server? If so how?

Service. Not "server." Servers are used on computer networks.

You can only use the device with Verizon or some CDMA carrier that supports or buys time from Verizon.

Your device doesn't use a SIM card. Verizon phones use CDMA technology, which doesn't use SIM cards. Only T-Mobile and AT&T in the US use those.