Change Name On Birth Certificate

I currently live in Canada, a Canadian citizen. However, I was born in Italy. I decided that when I'm 21 I'll change my name and first name legally, I'll change my surname from my mother. But will I still need permission from my parents to change my name a birth certificate, even though I already changed my name legally.

It is my understanding that you can not change what is on your birth certificate, no matter where you were born. You will still have your old name there, and new paperwork indicating the legal change of name to your new name. The situation is similar to getting married - you'll still have the paperwork to prove the old name in your birth.

I do not think you can change your name on your birth certificate.

To legally change your name, you must enter the courts -

You can then take the court, where you get your birth certificate and have a "new birth certificate" formed with the change of name

This is how its done here in the U.S.