First - when you are called - be polite to the debt collector. Here them out. Get their name, location and phone number.
Tell them, once you get the above info - you have the wrong person. They have no right to obtain your social security number from you.
If they continue to harass you during your phone conversation and continue to call you - keep a physical handwritten log of when they call - and the person's name.
You should then go over to the ftc dot com (Federal Trade Commission) website and download and complete their complaint form and send it Certified Mail/Return Receipt Requested (the green card) to the FTC. We pay federal taxes to fund the FTC - there is no charge to file a complaint nor have them hammer a collection agency or creditor for you.
You can the same if a creditor is harassing you at work. Obtain the name and place they're calling from - them verbally tell them - "I cannot accept personal calls at work. Do not call me here again." Then go to the ftc dot com website and report them as I've already described.
To really hammer on them - file a complaint with you State Attorney General's Office - you also pay your taxes to fund the AG of your state also. They will take care of the complaint.
You must teach these unscrupulous creditors a lesson - you may save someone else's job and credit rating.
By making the complaint and stopping them - you may be helping thousands of people and whipping these collection agencies, their agents, trainers and callers into shape to comply with the Fair Debt Collections Practices Act (the fdcpa).
Take care.
PS: If you owe the debt - no matter how long the original creditor hasn't contacting you - or a collection agency or law firm sends you a collection notice "out of the blue" - that doesn't matter - IF YOU CREATE A DEBT - IT'S YOUR RESPONSIBLITY TO PAY IT. The creditor should not have to "hunt you down" for you to pay your bills.
If you bills are too numerous and you can't keep up - you may want to consult a bankruptcy attorney. Filing a bankruptcy will cease all collection activity against you and it's not the end of your credit either. Don't let a collector fool you into thinking you can't list or file bankruptcy against your debts.
Only certain tax obligations, overpayments to you by a government agency, child support, maintanance/alimony, fines, parking tickets, student loans guaranteed by the federal government are not dischargeable in bankruptcy.