iPhone 5c - Problems

Hello guys, I'm very sad with Apple. I picked up because has good reputation, but I'm very unsatisfied. My iPhone 5c is not working as it should, and I bought at october!!! I can't to call, make movies, to use the recorder... it's impossible! The phone is locked! I need replace my cell phone because this is causing me a great inconvenience! I bought at New York but I live at Brazil. The support here is inefficient, I have already tried. It's my 1st iPhone, and if I can't replacing, I'll be very disappointed. I bought the phone with international warranty... 😠😟😢