No. A parent should not unilaterally change a child’s name without the consent of the other parent.  

If you change your child’s surname without consulting the other parent, there is a risk that the other parent will make an application to the Court.  This could result in an adverse Costs Order against you.

If there is a reason why the child’s name should be changed the best option is to seek the agreement of the other party or apply to the Family Court or Federal Magistrates Court for a Court Order.