I don't want to sound ungrateful but.....

Hi, my name is Mae and I'm 14. My dad has a yearly contract through work to have an iPhone and in February the year will be up so my dad said that he would buy the iPhone (I think it's a 5) off work and it will be my Christmas present. The problem is, I don't want an iPhone, I love my current phone - a Samsung Galaxy GT-I9000 (aka a Samsung Galaxy S1) - even though it is stark raving mad. My phone reflects who I am and I don't want to lose it. How can I tell my parents that I would prefer another Galaxy S1 over an iPhone 5 without sounding ungrateful and without hurting their feelings? ~ Thanks, Mae