You should probably get a lawyer's help.
If your felony is reduced to a misdemeanor, then you'll be off formal felony probation... so you won't owe supervision fees for the next 28 months, anyway. Even if you paid the fees in advance, you'd be entitled to a refund if the case is reduced.
A lawyer won't be emotionally involved with your case and can present this issue to the court in a calm, professional matter. When people try to represent themselves, they often become frustrated, which can lead the judge to think they are being uncooperative.
An attorney would also be able to prepare a motion explaining that your supervision fees were up to date, so the judge and DA would have all that information before your hearing on the motion to reduce the felony.
Please understand that this is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like this site, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.