My 12 year old daughter loves my husband and wants his last name(he is her stepdad),her bio dad only pays child support.How can we change her last name?

Let bio dad off the hook for child support by asking him to give up his parental rights to stepdad... thereby he loses all access/rights/support of his daughter, making him essentially no longer her father...

Then if bio dad gives up rights to daughter, have stepdad adopt her... thereby giving her the same last name... and essentially becoming her father. Be aware that if stepdad does take this leap, if a divorce should occur, HE would be the new father responsible for child support.