If I already had a court date and made a payment plan to the creditor and the judge okays the payment plan then I can't make the monthly payments,What happens next?Can I go to jail?

You will not go to jail.

If you can't make the payments, contact the creditor and see if you can work out a different payment plan that's easier for you. If you can't work something out then the creditor will get a judgment and they'll have the right to attach your bank accounts and/or garnish your wages until the judgment is paid in full.