I am travelling to the US soon and planning to get the unlimited text-message add-on ($15 for ten days). I don't want the outside-Canada data add-on plan. How do I adjust my settings to ensure that my in-Canada data plan is 'disengaged' from my cell phone so that I don't get surprise bills? I am using a Samsung Galaxy GT-S7560M phone. Sorry if this is a dumb question, but it's the first time I've travelled outside Canada with my phone.