It depends on whether there was an agreement to accept $1,500 as settlement, with just some final details to be worked out (and all evidence that you did or would accept those details), or if there was not firm agreement, just some discussion of a possible setttlement. In the former case, you could enforce the agreement; they can't garnish or take other legal action so long as you are complying with your end. In the latter case, if there was just discussion but nothing firm or accepted by both sides, they are allowed to go ahead with whatever other legal remedies they may have.If you feel they violated an actual agreement, you should go to court seeking an order that they return the money and cease other collections activities; in many jurisdictions (like NJ) this called an Order to Show Cause; it is also known as "injunctive relief."