If my son's Father re-sends paternity (denies it) can I change his last name to mine?

The for sure father of my 5 month old served me today with papers denying paternity by "re sending paternity", which writes him off the birth certificate as our son's father. I have a paternity court date for next month. During this time, he technically is not the father. So in this window of time, would I be able to change my son's last name to mine? I WILL be calling the office on monday to confirm, but I am anxious and would like to see what ya'll think. Thanks!