If i ask my lawyer to change the custody of the children from sole custody to joint, dont they have to?

  As an initial matter, your attorney is your legal representative and he/she owes a fiduciary duty to you. Among other things, your attorney must consult you about all settlement offers/proposals, and they must listen to your opinion. While your attorney may strongly advise you to accept a certain settlement or resolution to your case, if you say no, ultimately they must respect your wishes.   Your question says that you asked your attorney to "change the custody of the children."  An attorney cannot "change the custody of the children."  Custody of the children is ultimately determined by the court, either after a trial or by adopting the custody/visitation arrangements that the parties have agreed to and proposed to the court.  If what you meant was that you wanted your attorney to change the proposed custody arrangement, then yes, your attorney should do so.