Using the SURNAME OF THE FATHER?

I have a 13 years old daughter,me and her mother are separated for 11 years now and we are not married, she's using the surname of her mother until now, but she is in my costudy for 8 years now, I would like to acknowledge her as my child and let her use my SURNAME. Her mother and I agreed that our daughter's name should under my surname.since I'm outside the country I ask my sister to go to Cebu where my daughter's birth place is, and to process the amendment from the registrar office in cebu, but they rejected the application, they said that if we filed the application earlier this year maybe it's possible to process because its not very strict then. I'd like to know that is there possible for my daughter to use my Surname inspite of what they told us?

I already executed affidavit of acknowledgement to use the surname of the father and admission of paternity.

please kindly answer my query... please....?