Purchased iphone 4S in Norway (Europe) it usable in usa

I've recently moved to USA from Norway where i've lived all my life. Getting close to a year ago now I bought the new (at the time) iPhone 4S. Of course I brought this along with me. I've been living here for a week now and need to get a phone number fixed. As I now live in Montana, I heard tht there is not the best coverage here. I found out that Verizon Wireless is probably the best choice. I sendt them a email regarding my situation but they replyed; "Since all of Europe uses GSM-formatted phones, you iPhone 4S will not work on Verizon's CDMA-formatted network, as they are not compatible."

So does this mean that I cannot use my iPhone 4S anymore?! Or isit only Verizon that doesnt support GSM-formated phones.

Also I heard that iPhone 4S would support all types of networks? (might be misstaken)

(my iPhone 4S is legitimately purchased from the Norwegian apple online store)

Please, help is much appreciated!