Cache llc

Hello, I live in Washington State and just received a letter from the courts saying that cache llc had won a judgement against me for $6,000.00. I don't recall ever having had any interaction with these people. I did have a credit card debt about 5 years ago,but a law firm had contacted me and I made payment arrangements with them and made my payments for about 18 months. Then with out notice or a phone call or any thing else they quit taking my payments out of my checking account. I have not heard from any body on this matter for years and now I get this letter from this court saying that I owe 3 times what my original debt was. I thought that if you were being sued by somebody that you were supposed to be notified by the courts as to when you were supposed to appear in court to defend yourself against any false claims.I am a little concerned that far to many people are getting screwed over by companies like Cache llc, what should I do?