I guess you are using Samsung A790 or Samsung i830 on the Sprint network.
1. Sprint will, most likely, not let you roam on US GSM network (Cingular or T-Mobile). 2. E62 is locked to Cingular so even if Sprint actually allowed you to roam, the phone itself will reject your Sprint SIM card, because it is locked. I do not own E70 so I don't know.
Just in case you were new to mobile technology, Sprint or Verizon's Samsung A790 or Samsung i830 feature GSM services. Sprint and Verizon provide SIM cards and those phones have SIM card apability for GSM services on 900/1800. People are frequently asking if they could take those SIM cards from A790 or i830s and Roam on Cingular or T-Mo networks.
They seem to be understanding technology more than you think.
I knew that, and somoene who travels enough to have need of either of those phones would know that as well. However, somone who doesn't know the particulars of the wireless industry wouldn't. It's an honest mistake, what with so many phones being so similar and/or [seemingly] identical phones being carried by multiple carriers. One would assume they're similar.
That's an interesting thought, though - using traveling SIM cards from CDMA carriers for use on U.S. GSM networks. . . has anyone actually be able to do that?
if you get the phone unlocked for either Cingular or T-Mobile...you can buy rechargeable ($$$) SIM cards in the particular country and so long as the phone is Quad-Band, you can just drop in the SIM card and go. Your voice cost will be cheaper, but you might have a slight issue with data access (emails and internet).