These are not mystery shopping companies. They schedule shops on behalf of mystery shopping companies. Being in their data bases can get you access to assignments from many companies.
The links here are provided as a service to mystery shoppers. I do not charge companies to be listed. Although I screen companies before listing them, I do not endorse any of these companies. You should always exercise good judgment about giving out your personal information, online or offline. There are several articles on this site about avoiding scams, including how to spot a mystery shopper scam website.