Newbie questions.... Nokia 3315 to use in a few countries?

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I'm in Philippines right now and I want to buy a new (as opposed
to used) cell phone to use here, and in thailand, and maybe vietnam,
until I return to the USA in a few months. I'm seeing the 3315 being
sold pretty cheap (about $60). I don't need any "features" other than
being able to use the phone in a few different countries, mainly to
call back to the USA and access my voicemail, and maybe text messaging
(which i've never done before). So will this phone serve the
purpose...it's dual band, right? I guess the next cheapest NOKIA
around here in asia is the ?? 2100 ?? (also dualband). The freqs
used in these asian countries is 900 and 1800 I think. I plan to buy a
sim card in each country I go to...so that should work, right?
Actually, I wast thinking of buying a tri-band so that I can use it
back in USA and mexico (freq 850), but i've been hearing that it's not
easy to just buy a sim card in the usa (where I live, and use sprintpcs
anyway with an old qualcomm). I'm not sure what triband nokia phones I
would get anyway. Seems the triband model numbers start with the
number 3. ?