Not gonna work. But here is what will...
Convince them to take a look at the website in the link below, then use the products there to give your hair a break from the heating iron routine. You can have your curls look nice without frizz if you do this:
If you are going curly, you do this:
1. shampoo, rinse
2. deep condition (detangle) and rinse
3. work the leave-in throughout wet hair, then air dry (no towel or blow)
Once your parents see how you are trying to save time and money, and embracing your natural curls, then hit them with this...
Say, "I would like to go straight once in a while, so as not have to blast my hair with chemicals too often...so I want to buy a good quality ceramic iron on the net. But guess what (mom, dad), I can still use those great products you bought me on the net."
And here is how...
If you are going straight:
1. shampoo, rinse
2. deep condition (detangle ) and rinse
3. use a bit of leave-in on the ends, then do your heat
4. use a bit of MIxed Chicks Hair Silk once dry for shine.
BTW, according to Shape magazine, Halle Berry uses Mixed Chicks products.
Good luck. Probably better to become persuasive than sneaky. Those things usually come back on ya x10... Imagine, one day your own kid will be spending thousands on your card.
www.mixedchicks.net