If you send them a letter, in writing, demanding that they stop calling you, they are required by federal law to do so. If they don't, you can sue them in small claims court. Check out the FTC's page on debt collection here: http://www.ftc.gov/bcp/edu/microsites/moneymatters/dealing-with-debt-collection.shtml If you do decide to sue, you'll probably want to consult an attorney that does consumer protection work.
Of course, you still owe the money, and getting the debt collectors to stop calling you won't actually change that. If they can't get it from you voluntarily, they can sue you in small claims court too, in which case you'd have a judgment against you and they could garnish your wages.
Depending on how much it is that you actually you, you probably want to seriously consider filing for bankruptcy. Consult a bankruptcy attorney in your area.
This answer does not constitute legal advice and does not establish an attorney-client relationship.
A creditor generally has no right to have you arrested for simply not paying a debt. If a creditor is threatening you with arrest/jail, it may be in violation of your rights under Federal and Wisconsin debt collection law. I suggest that you contact a consumer rights attorney licensed in Wisconsin to discuss this with you. The National Association of Consumer Advocates maintains a member list of attorneys that can help you. I have provided a link below.
Generally, you can't be jailed for non-payment of a debt. We don't have debtor's prison in this country.
Get a recording program for your smart phone, and be sure to record all calls. When/if they threaten to have you jailed, ask them if that's even possible. Then take the recording to your local attorney.
I'm not your attorney; my answer to your question includes assumptions. If you want me to be your attorney, I'm easy to find.