Is email about returning a cable box a scam?

I received this email shortly after disconnecting my Comcast service this month (I've redacted my personal information):

But I've only had internet service for at least the last year, and I don't see a cable TV box equipment on my recent bills (I just had a flex box, which I returned when disconnecting my account). I called into Comcast customer service instead of the number in the email, and the representative confirmed that I did not owe Comcast any equipment, that my account was paid in full and fully closed out. 

I've had a bad past experience where Comcat's collections contracters called me to collect additional money after I had been told verbally by Comcast that I had paid off my account in full (it turns our the Comcast rep made a mistake, and didn't see that my final invoice hadn't been issued yet), so this is alarming to see this strange email and I don't want any risk to my credit, even though a rep on the phone said I'm good to go. I see other complaints of this same situation on the forums — can someone help reassure me that I'm not going to have an erroneous credit ding issued by "Complete Recovery Corp"? Also, are they fraudsters or a real partner of Comcast?

Thanks