I haven't done this but I would call the 800 number. Usually they direct me over to the credit delinquency guys right away!
But the only thing I have heard is that you have to keep track of them and make sure they are putting the correct info in your credit report. My ex stopped paying the mortgage two years ago for a few months and my score improves a little every month. Luckily we are about to sell the house. I will be glad when my name is off
I also get advice from Consumer credit counseling - the good one. https://clarifi.org/
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