800-586-8517

Would like to know the country of this number.

Why would you want to know the country of this number? Did they call you? You don't say ...
800notes is for unwanted phone calls, not for business or consumer disagreements.

The "800" area code is a non-geographic area code - the destination could be anywhere.

Search engines results found :

http://www.ripoffreport.com/reports/onechoicest1com/internet/onechoicest1com-its-a-bait-and-switch-what-they-put-out-on-the-internet-is-absolutely-1383212
But the complaint gives the wrong domain name for this phone number (onechoicest1.com is a parked domain).

There are at least two correct domains :
https://www.choicest1.com/
https://softstatus.com/
No business address appears anywhere either site.

One of the domains has a Facebook account :
https://www.facebook.com/pg/choicestone1/about/?ref=page_internal
No business address appears anywhere on any of their Facebook pages.

https://www.scamguard.com/choicest1com/
Gives two phone numbers for this website, one is the 800-number and the other is
85-26-181-8125

There is no country code "85" - however, there is a country code "852" and it is in Hong Kong.
Rewriting the number results in  +852-618-18125 where the "618-18125" is an 8-digit phone number and matches what Wikipedia says :
https://en.wikipedia.org/wiki/Telephone_numbers_in_Hong_Kong
Furthermore, the "618" prefix is a mobile phone number.

If you are having problems with the owner of this phone number, you need to contact a lawyer, and/or post complaints on websites dedicated to reporting such problems. One such website is http://www.complaintwire.org