How to convince my parents to get me a new phone?

I posted this yesterday and all i got was rude replies. So i will rephrase this. My iPhone 4 is constantly freezing and cannot even be used to text or call without freezing for 20 minutes. I would like a new phone and asked for one for christmas. They said no because i dont "need" a new phone. But i actually do because i do sports and need to call to tell them information, ie when to pick me up, the schedule was changed. Im not being a spoiled brat or whining to them. I just really need a new phone. We can afford it (and by we i mean my family), but my dad says phones arent worth the money, they might not be but they dont seem to understand that my phone doesnt work. When i tell them they just ignore me. Im aiming for an iphone because we all have iphones and my parents like the read reciepts. Any tips to convince them?