Hello All I am not an iPhone user, so I am seeking out the help of those who do use them. My daughter is on T Mobile and broke her phone, she wants an iPhone as her only iPhone is a Sprint model. I am going to have to buy one outright and am not going to do it at T Mobile. In your opinions, which model would be the most cost effective, a ,4, 4S, 5C or 5 also would it have to be a T Mobile phone to work properly? Thank You.