You should pursue child support. It is not for you, It is for your daughter.
If you wish to do a name change, that is a court proceeding. You need not have consent, but merely notice to the father. He will have an opportunity to come and object if he chooses. Notice can be accomplished by publication if you do not know where the father is. You ought to seek the services of an attorney who might be able to find the father and start up child support again along with helping you get your daughter's name changed.
There are many good lawyers oin your area. Speak to several and hire the one you like the best.
File a petition to change her name. It is not too hard but you might want to hirean attorney. He must be given notice and if he objects the court will hear the reasons on both sides and decide.
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