Different last name by choice

Good day, just want to ask f how can I change my last name. When my mom gave birth, my parents decide to use a shorter last name for my elder sister and i. (mahirap daw kc ipronounce s school) I know that this is odd so what my mom did is to secure affidabit for us and I am using the long last name for school records. Wen its time to get SSS, the last name that I register is the shorter which shows on my birth certificate. My parents last name that was on my birth cert is of course the short last name as well but what they are using is the long last name. Is it still posible to have it change to real last name which is the longer one.? Im afraid I dont have much resources of funds f this will cost much. I only have voters ID with my real last name and other ID's hve the last name on my birth certfcte. Thanks much. :-D

You can go to the LCR if they could consider you case as mere typographical error. You bring your parents birth certificate. Do not bring anything that shows your shortened surname. If its not a typo error, you have to go to court. File a petition for change of name. After everything, you can change all your documents, IDs etc to your real last name.