Well if youre taking lots of trips, your parents are acctually being irresponsible by not letting you have a phone.
but also they probably dont want to spend alot on a first phone for you.
ask them if you can have a really cheap phone. you can get decent ones for $15. just so you can be safe if anything happens while youre out. also tell them that if they catch you calling bad lines or run a massive phone bill, youll give them the phone back.
and once youve proven you can look after it for a few months and use it responsibly, BEG starting from about september for a camera phone for christmas lol.