In general, when it comes to your workplace, you should assume that you have less privacy rights than you would in your own home. This much should be obvious. But there are ways where this idea is trickier than others. So let's take a look at the rights you have as an employee when it comes to privacy.
First of all, the work space you use at your company belongs to, well, your employer. As such, they can search it whenever they want. This includes your computer and a company car, if they allow you to use one. State laws may vary on the topic, but the courts, in general, have been on the side of employers on this issue.
When it comes to emails and phone calls, you should again err on the side of caution as an employee. Any work email will be monitored by your employer. After all, it is their email platform. Additionally, if you use your phone for personal calls, they can listen in long enough to determine that it is a personal call and not suitable for business hours.
Another tricky situation is body searches. You may think these are strictly off limits at work -- however, that isn't the case. If an item was stolen or you work in a high-risk security area, then a search of your person is usually allowed at work, so long as it isn't too invasive. But frequent an unwarranted searches of employees just for the sake of it are not acceptable and probably illegal.
Source: FindLaw, "Privacy at Work: What Are Your Rights?," Accessed Sept. 19, 2017