What are my options if I got a letter in the mail saying I violated my probation?

My mother got a letter at her address summoning me to appear for a probation violation hearing here. I have been doing all my classes, and following the probation requirements to the T. The letter gives no reason as to why it was violated it simply says that I am to appear in court. I have been taking classes for my anger issue and have missed a few (and my PO is aware and never seemed to care since I was missing them in favor of staying employed). My probation was extended under the promise that I wouldn't have to go in front of a judge if I mutually agreed to get it extended. I am less than a month away from finishing my classes. The only thing I haven't been able to do is pay the outrageous court fine (I was told failing to pay it would not endanger me from jail, it would just be sent to collections where I could set up a payment plan). I am not sure what I did wrong.