At least in Texas, after serving time on probation, and completing all requirements except the balance of the months required to report, courts can place a person on unsupervised probation. However, there may still be costs associated with such action as the probation office continues to have to conduct work on the case. (The probation fee is to help with the costs that the county incurrs in supervising probationers.)
If your probation officer cannot or is unwilling to make this request of the judge, you should hire a local lawyer to talk with the judge. If you go to a big firm, ask for their newest associate, or hire someone you know has a low fee or is new. This is not a hard task you are asking, and if granted, it will likely be worth the money you invest as you will save on the probation fee.