Privacy in the Workplace FAQ
Can I monitor my workers' phone calls to make sure they are properly serving my customers?
4. Can I monitor my workers' phone calls to make sure they are properly serving my customers?
Yes, with a few limitations. You are legally allowed to monitor employee conversations with customers for quality control. Federal law allows you to do so without warning or announcement, although some states require you to inform the parties to the call in some way that you are listening. However, you may not monitor personal calls. You must stop monitoring once you realize that a particular call is personal.
For more information, see Nolo's article Monitoring Employee Communications.