Help change my contact name after using a different Apple ID to activate iPhone.

I used my sister's Apple ID to activate my iPhone 6 since whenever I use mine, it doesn't work. Everything is good but when I click "Contact", her name is the one that appears on the very top (above the one that says my number). Please help me change it to my name instead of hers. Basically, my phone is it registered on my Apple ID. I don't want to reset my phone anymore since I have important files and stuff in here.