Collection... "very important you call this number immediately"

This is a debt collecting company. Some of it is legit, but the debt they are calling me about has already been paid. They also have not sent over the documentation I asked for yesterday. Just be very careful when calling them back, if you decide to. Also the debt they are trying to collect on is almost outside of the SOL.

They did not identify their name or company, just stated it was in reference to debt collection, and that I should immediately call 877-590-9066.  Since I have no outstanding bills, I'm not calling them back.