My boyfriend is in jail right now and there was a conflict between his public defender and him we are looking to replace him but how would we do that ? And is it to late because his court date is on Wednesday

Really too late, unless you don't care if a unprepared PD shows up for court. In some places, if it is a minor crime of course often you never know which PD will show up, and just work off the notes form others who did the research.

But there has to be a serious conflict that would effect his ability to defend the person.
He( person in jail) would contact the PD office and ask them to re-assign a new person.
For serious he can "fire" the PD, ask the judge to re-assign a new one.

Of course what you will have is one of his friends, who may have an attitude about you firing their friend.