The only thing that will stop a garnishment is Bankruptcy. Sorry. If it is hurting you that bad financially you may want to consider CH7. Most lawyers will give you a free consultation. It doesn`t hurt to at least get some legal advise and explore all your options.
I live in the state of PA. ( I think?) the only way a outstanding debt can be 'garnished' is if the debt is a Federal Loan that is outstanding (ie..school loan in default..) or something to do with owing the IRS. You have to decide what 'method' works best for YOU. Everyone's situation is different.