Unfortunately, the creditor is not bound by the divorce decree. In other words, you still owe the debt, even though your ex-wife has promised to pay you for it. So they can continue collecting.
You mention that it has been "many years." Depending on how many, the debt may be outside the statute of limitations, though. They can still try to collect, but they cannot sue or make threats of suing you, if that is the case. You should talk to a consumer lawyer to find out.
In the meantime, make sure you take careful notes of all communications from debt collectors, record phone calls, if you can, and contact a consumer lawyer in your state. And check the links below for more information.
With regards to your former wife, if she did not follow the decree of dissolution, you may be able to file a motion with the court to enforce the decree.
Depending on the amount of the debt, how likely you can collect from her, and various other factors, the effort may not be worthwhile.
Your situation is why clients are often recommended to make a clean cut when there is a dissolution of marriage. Each party should refinance the party's awarded assets and debts into that party's own name.
You may want to review your facts and options with an attorney.
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