Product: Debt collection

On XX/XX/XXXX I accessed my payroll for XX/XX/XXXX ( appears on self service the weekend before it is paid out ) and noticed a garnishment appeared on my check in the amount of {$470.00}, I contacted the payroll department and they told me to contact Gurstel law Firm. On XX/XX/XXXX I called and spoke with XXXX, he stated there was a judgment from XX/XX/XXXX from XXXX XXXX, I asked what it was for, he could not answer that, I asked why I was never notified and he said in XX/XX/XXXX they mailed out the intent to collect a debt, he stated it was mailed to a XXXX address and they had my maiden name on the file ( I had lived there 22 years ago ). I informed him I had no knowledge of this debt and I had just applied for a mortgage and nothing appeared on my detailed credit report, he told me I had to pay it or state it was fraud, I told him it was fraud and gave him my current address ( XXXX XXXX ) and he said he would mail paperwork. 
On XX/XX/XXXX I called them back ( XXXX ) and spoke with XXXX, and told her I still had received nothing from them, she stated there was nothing in the file and she was unable to validate the debt. She stated she would do some research as there was nothing in the system to validate the debt and call me back. On XX/XX/XXXX I again review my paycheck to see if anyone had cleared this up and a garnishment of {$470.00} was again deducted from my payroll. On XX/XX/XXXX I met with The attorney who helps XXXX XXXX with legal issues ( my husband is currently a XXXX XXXX  receiving XXXX at XXXX XXXX XXXX and XXXX XXXX ), she was going to review the case and see if she could help us out, but she recommended I call again. So on XX/XX/XXXX I called and spoke with XXXX who stated he saw that I requested information and Id have to wait for it, I again explained that I have never received anything ( no communication what so ever before the garnishment ) he asked me to verify my address and I did, he then stated that all the communications and documents had been mailed to the XXXX XXXX address, I told him that I changed my address on my 1st call, but he argued that they had always had the XXXX XXXX address. I asked him to please put a hold on the garnishment until this can be resolved, he then asked me if I needed anything else because he gave me all the information he was going to. I requested to speak with an attorney for the firm, he said they were busy but would send me to the voicemail of XXXX ( an attorney ), I left a detailed message for XXXX but did not receive any communication back. 
I am in the process of refinancing my home due to my husbands illness and inability to work, this has caused a delay and increased our hardships. I have asked that they stop the garnishment and if the debt proved to be validated I would take care of it without payroll garnishment but NO one can tell me what I purchased, where I purchased it, when I purchased it just that it was XXXX XXXX, just that they they are collecting {$3100.00}. I was Never notified, never contacted, never given to option to ask questions, never allowed to respond, they just started taking my money, and they tell me its perfectly legal- and they will continue. I need to know how this is legal?