I live in the Chicagoland area as well (just South of Joliet) and I get unlimited 30mbps LTE. I know T-Mobile's still in the process of upgrading its network, but as far as my area goes, I have no problems with signal. I'll be putting my phone to the ultimate test next week when I drive to Houston for the third year in a row (Missouri and Arkansas were TERRIBLE to drive through the last two years as far as reception goes). I don't know how long you plan on having yours if you get one, but since T-Mobile announced that they're acquiring some 700mhz spectrum in the future, I'd get the C6806 if I was just now going to get one, since the C6833 doesn't have a 700mhz radio.
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