I am called several times a week, sometimes 4x in the space of two hours, by a company from the number 888-913-2337. When I pick up, half of the time I get a hangup. Another 48% of the time, they respond and I ask what this is in regards to. They hang up.
A few times, they have mentioned me being in debt to Washington Mutual for a "very small amount", but they quickly hang up.
Once, I talked to a guy more in depth. I told him I have never done business with Washington Mutual (they only entered my geographic market two years ago).