It's not outlandish to think that if, say, your parent bought a vehicle for you to use, and they held the <strike>title</strike> title documentation and lien note... while they were making payments on it on your behalf, and you were driving or in possession of the car when they died, that it follows logically that you should simply assume that debt and maintain an uninterrupted record of payments in order to be able to continue uninterrupted use of the car. Stretch that example to "a car that was bought with a credit card" and you can see how this could be a legitimate effort. I don't know how that plays out legally, but I assume there's not any legal option where the debt simply goes unpaid by the estate and by you, and the car is not legally meant to be repossessed.

You may not have known that the car you are driving is not paid in full. Large assets can be repo'ed if the account that paid for them is in arrears. This is not necessarily going to happen right away, the estate may have accounted for this already, there are plenty of reasons why this contact is bogus, but it could also be possibly in your interest to follow up with payments in certain cases. (Fight me?)

You could give the car back to the estate (probably the right answer?), or argue that it was a gift, and the estate should pay for it, but I don't know if either of those arguments will actually get you anywhere / prevent the car from being repossessed. You might have documentation that it was a gift, but there's also a lien on the title. Your gift might have been smaller than a car, there's no title, and you might not have any documentation of the gift. (I'm not sure if it matters that you can prove it was meant to be a gift.)

It's probably not considered harassment or illegitimate on about the same basis that you can be newly considered responsible for your own debts that are "past the statute of limitations" that you have started payments on again, even if your last contact was some time after the statute of limitations had already expired.

At that point the debt collectors can continue contacting you, but the collection efforts must include language that explains the fact that you can't be sued for these debts. Well, what they don't explain is that by making a payment, you could be resetting the statute of limitations and newly assuming responsibility for the whole debt, with a brand new expiry date. (I am not a lawyer and this is not legal advice, but this is my understanding of why you "just don't answer those letters.")

You wouldn't have started making payments if you didn't feel that you ought to be responsible for the debt, "QED." Not saying it's fair or right, but there are cases where that's what the law assumes and approximately why it is so.

There are also a lot of things that collectors can do, that would easily be considered harassment if you simply asked them to stop (and then they persisted anyway). People don't always ask, or know that they should ask. Especially if they don't want to pay! (Whether or not responsible, it rightfully makes people go on the defensive to receive a contact from a bill collector.)

I'm getting downvoted but nobody is telling me if I've said something incorrect. That "disagree" button...