I wasn't home to answer. No message was left. It could be just a coincidence but SOIL happens to be an abbreviation used for/by Special Olympics of Illinois.
"Hope this helps" nailed it. It appears that Special Olympics of Illinois has several different caller ID's set up on thier fundraising phones (SOIL, Sp Olym of IL, Medallion, and probably others). We get about 2 or 3 calls from their various numbers EVERY day. If you check the actual numbers, you'll find that they are just a few digits apart, obviously all from the same call center. Perhaps if they would stop paying people to harass us with these phone calls, they would have enough money for the kids in the special olympics!