I worked for a British taxi company that was developing that kind of app, I developed it. One problem for the company was that their drivers worked for Uber at

I worked for a British taxi company that was developing that kind of app, I developed it. One problem for the company was that their drivers worked for Uber at the same time as them. They were freelancers, not employed by either firm. They had two phones one for receiving jobs from the taxi firm and the Uber one. We had to trust that they weren't doing both at the same time. I think they used Uber to give them work during periods when it was quiet for my firm. Does this double working happen in the USA?