Since you are still at the pretrial stage, your current plea is not guilty. You would not want to change the plea because the only other alternatives would be guilty or no contest. Stick with a not guilty plea for now. But yes, you can keep your plea of not guilty but obtain a new attorney. You should do that quickly though. Judges don't always like to let attorneys swap out if it delays the case.
If you have a public defender and you want a new attorney, but still one paid for by the state, then it is not likely the court will let you do that unless you can show that somehow the current attorney is basically incompetent. If you have a private attorney and you simply want a different private attorney, then go out and hire the new attorney. The new attorney can file a motion for substitution of counsel and the judge would likely allow the current attorney to withdraw. Your new attorney would likely ask for a continuance, waiving your right to a speedy trial if it hasn't already been done, but that could be up to the judge.