Calls from 877-787-9860 are definitely from the Census Bureau.  I just got off the phone with them.

https://respond.census.gov/awts

Called claiming to be Census Bureau

I've got about 25 calls from these knuckleheads, They too claim to be from the US Census Bureau. However, on Caller I.D. it always shows up "Unknown name, Unknown number." They give me some long case #. It annoys me since they NEVER say what the problem is. I've sent in my census form months ago. If there's a problem, state it in your phone message or better yet, if they claim to be from the US Census, you have my address, send it "snail" mail! They're as bad as telemarketers!

I just called the Census Bureau using the number listed on http://2010.census.gov/2010census/how/preparing-for-a-census-call.php and HE VERIFIED that they have NO IDEA and NO CONNECTION with 877-787-9860 or the number shown on my caller ID, 812-218-3144
. He ALSO confirmed that Census Bureau case IDs are 8 digits long with no characters, whereas these scammers were giving me a 7 digit/character ID AND it varied between their calls.