Blank Surname

First of all, I shall give these pseudonyms to better explain things:

Name on BC:

First name: Mary Anne
Middle name: Santos (from mother's maiden name)
Last name: (blank)

Mother's MAIDEN name:

First name: Jane
Middle name: Reyes
Last name: Santos

Father's name:

First name: John
Middle name: Cruz
Last name: Santos

My parents aren't married, however, they do have the same surnames. My mother said that the nurses in the hospital I was born in didn't put a surname in my BC because my parents aren't married. But my older sister, who was born in a diff. hospital, has the same middle and last name as my mother. I would always follow hers and use 'Mary Anne Reyes Santos' in all of the documents and school papers I fill up. I have never encountered problems. I was issued a passport in 1995 when I was 2 years old. But when it expired and my mother tried to apply me for a new one 5 years ago, DFA said we had to fix my birth certificate first. I remember she went to Mnl City Hall numerous times but they keep asking for more and more documents every single time she came back to submit the previously required ones. She gave up eventually. But I'm 19 now, so I think I can try to fix it myself. I don't know how though.

Question:

Is it possible to move Santos to my Last Name and put Reyes as my Middle Name just like my mother's and sister's? Will it take long and cost much? I really need my passport by the end of March.

Thank in advance.

Yes it is possible but through COURT ORDER, the law says that no entry in the records(records in the civil registrar, which includes, birth certificates) be altered, modify or change without court order.

How long? depending on court's workload
How much? depending on lawyers fee