How do I convince my dad to get me a new phone?

I've wanted a new phone with texting for AGES now and he just doesn't seem to budge. I think I have made a small break-through by printing out information on the LG VU (the phone I really like) And he said "I'll look into it" however I really need to convince them that I can handle texting and it won't break the bank. I have thought about the whole, unlimited but that's 20 a month. Any opinions on how to push them to say yes to a new phone? And to veto texting? btw I have AT&T