Alpha, you reminded me of something.
In Canada, there are laws that limit the number of times in a day that a collector can call: 3. And once the debtor says, "please don't call me again", they cannot legally call them again. They can still send mail and whatnot, but not call.
The dodgy collectors don't give a rats patootie and will call dozens of times a day. Even if they talk to the debtor, they keep calling back, and calling back, and calling back. This amounts to harrassment. But, you know, the dodgy collectors don't care.
When a debtor declares bankruptcy in Canada, a collector can no longer contact the debtor in any way at all, and can no longer issue garnishee orders, repossess vehicles, seize assets, and so on. The dodgy ones will anyway. The assets will eventually be returned to the debtor - a month or two later after court cases - but the dodgy collector doesn't care. He's spiteful and vengeful and likes making life as difficult as possible for the debtor.
A bunch of years ago, I had a roommate who went missing. I reported her to the police, and it was when the cops showed up that we (the other roommate and I) learned that she had a history of identity theft, fraud, and forgery. She'd put the utilities into my name without my knowledge or consent (impersonated me over the phone) and racked up the phone bill by calling all over the world. It took two years, despite presenting the police file number, to get the utilities to remove those debts from being in my name. For two years, I was hounded by debt collectors trying to collect a debt that I had not incurred. And I repeatedly told them the police file number, the circumstances, and told them not to call again. They didn't care.
Same as the debt collectors who were calling about her debts. Tell them she doesn't live here anymore, we don't have any forwarding information for her, here's the police file number, and don't call us anymore. That went on for two years as well. Debt collectors didn't care. They harrassed us for her debts, refusing to believe that one of us wasn't her.