CAn ChecknGo garnish wages?

I had a CA internet installment loan through checkngo in 2006 and a someone from an attorneys office called my job stating they were garnishing my wages. I asked them to send me something in the mail and not call my job to prove I owed about $400, as I thought it was paid off. The unidentified lady stated she did not have to send me anything proving this. Then an un-named guy from the same place called my job again the next day asking for my payroll department and I refused to give him that info then he call my house and spoke to my mother telling her that he was garnishing my wages. CAn they do this and are they allowed to tell other people about any supposed debt I have.