With respect, justifying the creditors actions because the problem (or, if you prefer, fault) lies originally with the debtor rather misses the point.
The creditor has every right to attempt to recover the debt owed by the debtor, but not by any means. One of the means that, by my interpretation, is not permitted, is persistently calling persons who have no relationship with the creditor.
If I have new slates fixed to my roof and I don't pay the roofer, the roofer is not entitled to come around and strip them from the roof - irrespective of how we may all feel about the moral issues. It is not a question of morality, it is a question of law. The roofer must try to recover his losses for the breach of contract by taking court action against the party who owes them a debt and add the costs of doing so to the grand total being pursued. I'm afraid that's how it is for our nice bankers. A well know source of moral virtue. What they cannot do is harass people - especially those who have done absolutely nothing wrong.