I am with rogers and just got a new phone. You should ask them, because at certain times you are able to upgrade without paying anything, but if its not one of those times you will have to pay more. But no, you dont have to change your plan to get an upgrade. It also depends how much you pay by what teir you are on. I was on teir 5 (the highest), then I upgraded to a blackberry and that makes your teir go down so now I am at teir 3, but I still didnt have to pay anything for my phone. Your plan would stay as is.