Persuading skills for iPhone?

My dad has an IPhone 5 at the moment and he is on a contract. I however have a little Samsung Galaxy Ace which is very close to breaking. I have about £100 in savings and I want to buy it off my dad. He is reasonable and he hardly knows how to use it like a proper IPhone 5 owner. I'm very responsible (I didn't break my phone) and can look after it. How do I persuade? I tried by saying I'll do extra stuff around the house, on my best behaviour and not being rude to my siblings. How else do I persuade him?

You threaten him.

Okay, stop mentioning the IPhone for AGES like a month or more, it depends how easily your mom is proud of you!
In that time, start, tidying up for your siblings, looking after them, Helping them with homework/ playing with them. Try to offer to hoover or set the table. Get good marks at school.

Then when the whole family is together, eating dinner, not when they are concentrating, suddenly drop in the IPhone conversation, and talk about how much you wanted, for example,

Your school report comes and is great. Your parents congratulate you, then as soon as you can mention the IPhone.

That will get you somewhere, and they will think you deserve it!