For several years before I retired in 2011, I had an account with Racing and Gaming Services (also known as RGS). I also visited their operation in St. Kitts and talked with everyone from their very efficient phone operators to their executives.
These days, California players cannot bet California races via RGS. There are other restrictions for some other places, as well.
While the majority of their handle comes from computerized robotic wagering, they do have many customers who simply call their bets in by telephone, just as you would do with your local ADW.
The normal betting requirement to use their services is $1 million per year, though there may be some exceptions.
To get further information, go to their website (
www.rgs.net) which lists their phone numbers and contacts.