Change my surname to my biological father's surname

Good day! Hihingi lang po ako ng advise kung anong proseso ang dapat gawin para mapalitan ko ang surname ko. Kakaalam ko lang po kasi na yung nakapirma sa birth cert ko at ginagamit ko ngayong apelyido ay hindi ko totoong tatay. Inamin na po ng nanay ko sakin. Nakilala ko na din po ang totoo kong tatay. Ano po ba ang dapat kong gawin para magamit ko yung apelyido ng biological father ko? May anak na din po ako at gusto ko din po sanang mapalitan yung apelyido niya kapag napalitan yung apelyido ko. Yung asawa ko po ay maiden name pa din naman ang gamit niya kasi inaantay din niyang maayos legally yung surname ko. Sana po ay mabigyan ninyo ako ng legal advise. Mga magkano din po kaya ang magagastos? Salamat po.

Up....
Baka po may lawyer dito na pwedeng makapag advise regarding sa situation ko po. Hoping po for your response. thank you.

were your mother and the one who signed married?

Yes they are married po. But i havent met that person po

same answer as here: http://www.pinoylawyer.org/t33187-change-my-family-surname-to-my-biological-fathers-surname#138165

Thank you po for the reply. So kung mahahanap ko yung "father" na nakalagay sa birth cert ko at sasabihin niya na hindi niya ko anak, pwede pang mapabago yung birth certificat? Possible po ba na ipa DNA test ko na lang yung totoong tatay to prove na siya yung tatay?
Another question po, bale nagkausap na kami nung totoong tatay ko as per what my mother said, kaso yung statements niya at ng nanay ko eh magkaiba po. Seems they are protecting their own interests. Possible po ba na iakyat sa court tong situation na to force them to tell the truth and finally settle this once and for all? What kind of case po kaya?

as i said in the other post, only the husband of your mother can question whether you are his child or not. and after you became 1 year old, he can no longer do so.

you do not have a legal remedy available to you. as far as the law is concerned the husband is your father even if you are able to get a DNA test.