It is very complicated, I think you may be able to transfer after you spend 45 days in your "matched" program, provided both program directors will be ok with it (unlikely) and some other details that I am not aware of.
Match is binding only in so much as the NRMP can label you a match violator.
Theoretically if OP found a spot and a willing PD they could just bail on the prelim spot. But doing so would label them a match violator and get them banned from the match, so they better be darn sure about their plan.
Practically speaking it is extremely unlikely any PD would hire someone in this circumstance.