change of surname

i want to change the surname of my SON.the father of my son is already married to someone else before we have our son.but when my son was born i use the surname of his father and he sign in the birth certificate of my son.my son is already 3 years old and for 3 years right after i gave birth I DONT HAVE COMMUNICATION already to the father of my son and he never support us at all.now what i want to do is to change the surname of my son into my surname.what is the best legal matters i should take?is it possible that the surname of my son will be change?how long does it take?is is a long process?PLEASE HELP ME..looking forward to your reply.

http://www.pinoylawyer.org/t2632-childs-change-surname