Employers may limit employee rights and personal freedoms. However, that does not mean that it is possible to completely ban the use of mobile phones during working hours.
No, it is very dangerous to generally and absolutely ban the use of personal telephones.
The limits should be justified by the nature of the task being performed and proportional to the purpose pursued (Labor Law, Art L.1121-1).
The rules of procedure cannot be justified by the nature of the task to be performed and may not include restrictions proportional to the purpose pursued (Labor Law, Article L.1321-3).
However, for safety reasons, you may prohibit the use of the telephone while driving equipment, handling dangerous products, or when there is a risk of interference with electronic equipment. However, employees working alone in the office are prohibited from using their mobile phones. The phone doesn't seem to be justified.
Using cell phone jammer can be annoying to other employees. Therefore, it should be used with caution. For example, you can set usage rules such as asking an employee to put the phone in vibrator mode or making a call outside the office.
Commission Nationale Informatique et Libertés (CNIL) permits its use for personal purposes within the company, provided that the telephone and the Internet are reasonable uses.
Remember that employees fulfill their employment contracts in good faith. You need a reason to use the phone. Don't sacrifice work performance. In case of abuse, employees may be punished. You need to be able to prove the abuse of your personal phone during working hours ...
To accurately determine the scope of your rights in disciplinary action, Tissot Editions advises the document "Tissot Social Enterprises", whose complete file is dedicated to "disciplinary and disciplinary action".