Most of the time, it's better to settle with a debt collection agency rather than letting them take you all the way to wage garnishment.
But the biggest factor in this is . . . you need the money first. Typically, debt collection agencies will settle 25-40% on a debt (but not all the time). Take the total owed and figure this amount. If you're able to save this amount do it. Then, call them.
It's going to take a lot more than one phone call or letter to accomplish this . . . so you'll have to be persistent. Because, it's always better to settle than force them to garnish your wages. Check with state's Attorney General's Office on the maximum amount allowed. As of this writing, in Minnesota, this amount is no more than 25% of your gross wages.
**Please keep in mind, the advice given above is only my opinion, and your situation may be different so it would be adviseable to seek legal counsel**