My wife uses Tmobile and they recently have gone unlimited text and web and 20cents per minute talk in Canada (and most of Europe). Of course, unlimited everything while in the US. Though they throttle after 2.5G of data use.
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She pays $70 unlimited for both countries and it's seamless. I have a Wind plan up in Vancouver and straight talk down here which is over $100 for both so I'll switch to Tmobile pretty soon here.