Cingular national coverage: Cingular web site info doesn't match letstalk.com info

Hope someone out there can clarify this for me:

When I go on letstalk.com and research their Cingular family talk plans, the map that they show of Cingular's nationwide coverage does not match the map that Cingular shows on its website.

Letstalk.com's map shows a much WIDER and comprehensive coverage - it's what I want. Why doesn't it match Cingular's?

Does this have something to do with the types of phones that letstalk.com offers? Are they somehow "unlocked" so they can roam without charges across the US?

I'm currently on Cingular's Nation plan that it offered over 2 years ago (using a Nokia 3360). The service area that I have with that plan is exactly what Letstalk.com is showing (and therefore what I want to keep). But when I go into a Cingular store and ask, they tell me that they don't offer that service area anymore because they only offer the new GSM phones that don't have the same service areas as the older phones.

Basically, if I go with Letstalk.com, am I setting myself up to get scr*wed somehow? They offer awesome deals - nearly too good to be true. I don't understand how they can offer better coverage than Cingular.

Thanks.

Letstalk might have an older map.