Switching SIM between two phones.

[cne]

I currently have a Nokia 6340i with Cingular in N. Florida on their old Preferred Nation Plan. I just recently bought a Cingular Nokia 3595 from a friend and place my SIM card in it and it works fine. My question is, since I'm on the preferred nation plan how is roaming going to work with this GSM only phone. Will it still read out "Cingular Extend" to let me know I'll be paying roaming charges when I travel out of state?? I realize I won't get as good of coverage with the GSM only but just curious if it would even work. If not I guess I'll just have to put the SIM card back in the 6340 before leaving town. Thanks for your help!