If you have to participate inn csab then do not withdraw from josaa as whatever fee you would have paid as seat acceptance that will be carry forwarded and in csab you will just have to pay the registration fee only and you will be able to participate in csab also if you get a  seat then no more fee has to be paid in your case and you can either accept or withdraw in 1st round but in second round you will have to accept only and you will have no other option and you asked about withdrawal from josaa round 6 then you cannot do so as if you decide not to join then your fee will not be refunded.