1. You are out with your friends, and your parents need a way to contact you without going through your friends. What if there is an emergency and you are alone without a phone?
2. You think because you're growing older you deserve the privilege and you think you need privacy in terms of phone calls because you think you are mature enough.
3. [Optional] Suggest that you get a job in order to help pay for the bill. Either that, or you'll do more chores to help pay for the phone.
4. Have a list of phones that are affordable and easy-to-use. Find the cheapest plans and whatnot, if your family is not already on a plan.
If they don't let you get a phone, be patient. You will get one eventually. As I said: do NOT complain and do NOT be snotty about it. That gets you nowhere.
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