You should notify the attorneys formally, in writing, with some record that you did (fax receipt, certified mail, etc.) that you are terminating their services. Request a motion to withdraw that you can sign off on. You do not want them spending any unintended time on your case and they will remain your attorney of record until the motion is signed by the judge. Further, request a date certain that you can get your file from their office.
You either retain new counsel who can file a motion for substitution of counsel or you can ask your attorneys to withdraw from the case, which requires them to file a motion to withdraw.