I had to order mine separately from my carrier, but I verified with them that they could activate it and all that - I think you’d use the same SIM card and therefore wouldn’t have to change your number but I don’t really know how that works. When I’ve had to change phones I just tell the people at the carrier store that I have certain red lines I absolutely will not cross (budgetary and otherwise) and whatever their misgivings or confusion they’ve worked with me on that. They still try to upsell me whenever I have a technical support question, of course.