Respectfully, your inquiry is puzzling. If you were sentenced to probation, you cannot sign a document and avoid it.
Wisconsin law did recently change, though; and the Department of Corrections may now release you from probation after you serve at least half your probation term. It used to be that you had to file a motion in court for such treatment.
If this does not answer your question, I suggest you repost and clarify.
I agree with Attorney Missimer. It could also be that you are referring to revoking yourself from probation, although again, your question is not clear. If you are sentenced to probation with a condition of jail time, but with to simply serve jail time without serving probation, you do have the option of revoking yourself from probation. Before taking such a step, I would highly recommend that you consult with a licensed attorney to determine why you are dissatisfied with probation, what if any options you have for adjusting the conditions of your probation, and what amount of jail time you are facing upon revocation.
If you are revoked from probation, and your case is a misdemeanor, you will most likely be able to serve your jail time and upon release be off of probation. Again, please consult with an attorney to evaluate your specific situation before signing any papers if you are on probation.