QI am responsible and I think my parents know that already. I am 15 and I already do the dishes, laundry, I vacuum, dust, get excellent grades, I baby-sit my sister constantly, and I also do not do drugs or drink alcohol. I guess you could say I am "perfect," but aside from all of this, my parents will not let me go out on a date with a guy. They will not let me go out with my friends either! I just want to go out once or twice a week, but no! I have to baby-sit my sister all the time. She follows me and my parents don't do anything about it. She is also afraid to be home alone (supposedly.) And one more thing, my sister made a long distance call that cost about $35 and I had to pay for it! What is up with that? Why should I have to pay for it? PLEASE HELP!
I'm sorry that life is so unfair for you right now. Your parents are, most likely, only doing what they think is best for you. They probably want to protect you from everything, but talk to them (calmly) and tell them that if they don't let you start doing things on your own and earning trust that you aren't going to learn how to handle things on your own, which you will have to eventually anyway. They should be preparing you for the real world, not hiding you from it.
It really sounds like you're a very dependable person! Your parents might be taking advantage of that. Your sister is their child, not yours. They shouldn't leave you to watch her all the time. Explain to them that you don't mind watching her every so often, but you need to have a life, too.
Ask your parents what more you have to do to earn their trust. If they won't allow you to go out with your friends, ask if you can invite one or two friends over to watch a movie or something so that your parents can meet and get to know them.
I really don't understand why you had to pay your sister's phone bill. Did they think you had made the $35 call?
Maybe it would help if you outlined all of this in a letter to your parents. That way, you won't say anything you regret, and they can digest it before reacting.
I hope that my suggestions help.