How do i find where telephone prefix 866 is from?

keep getting annoying messages on answering machine

If you get called by numbers and area codes that you don't know, just type it into a search engine (google and yahoo work best) and it will generally give you the information you need. Just type in "866 area code" into the search box and see what you get. it works for about every number.

That is a toll free number.

866 is an 800 number

An 866 number is the same as an 800 number. I heard that they ran out of 800 numbers so they have to use others. I've seen 866, 877, & 888.

It's US/Canada Toll Free...Probably telemarketers.
Get caller ID...

An 866 number is a toll-free number and it could be originating from anywhere in the US. Even you were to track down the location of the call center you would have a hard time tracing the person who made the call.

866 is toll free as well as 877, 888 and 800. There are some new prefixes set aside for toll free numbers but I dont think they have been issued yet.

From Wikipedia:
North American Numbering Plan are sometimes called "800 numbers" after the original area code which was used to dial them. They include the area codes 800, 888 (since 1996), 877 (since 1998), 866 (since 2000), 855 (since 2000 although not yet in use), 844, 833 and 822 (the last three are not yet active but reserved).

The following area codes are toll-free and numbers using these area codes can be located anywhere within the North American area code numbering system.

800
866
877
888

"Future" additions will be:

855
844
833
822