changing of child's last name

hi! i also want to seek advice regarding the changing of my son's last name. I am not married to my son's father but he acknowledged him and he's using his father's last name, now his dad got his own family now and has kids with the new partner. I want to change my son's lastname to mine since I'm not getting any financial support from the father ever since, it was my ex's parents who gives some amount to me for their grandson (my child), as per reading the thread here, is it still the same that I need to adopt my son to have his last name changed to mine? im just quite confused on that part and what should i do? do i also need to have my son's father consent? thanks.