Hmm I think you can get it straightened professional which lasts a couple of months, will try and remember what it's called.
Greatgooglymoogly - find a shampoo which doesn't have SLS in it. When you wash your hair only wash the scalp with shampoo (using fingerpads) and length of hair with conditioner. If you do wash your hair everyday then use shampoo and conditioner one day then just conditioner the next. Use a clarifying shampoo once a week. Don't rub your hair when you get out of shower/bath just wrap in towel. Do not use comb/brush. Spray leave-in condition in it and then use a curl creme (I love the pink boots one) rub it in your hands until it emulsifies and then run your fingers thru your hair. Leave to dry naturally.
Ah that's the one, my flat-mate used to have it done as she had thick curly hair, however I have to say as much as it was straight it didn't look like the swishy straight hair that girls who are born with straight hair have. Are you sure you can't embrace the curls?
I have a secret. I have very very thick curls, pube-like in condition. I have a wet-2-straight straightner which is bloody great, somehow it makes my hair shine like no other straightner. I never use it on wet hair, only dry.
I had mine professionally straightened, I think it was called Wellastrate. Had it done 3 months ago and it still looks just as good, I literally just wash it and leave it to dry naturally, it's a revalation! It cost £100 but so worth it for me.