Mobile jammers are generally not approved by the government

The working principle of mobile phone jammers is similar to that of jammers because the radio frequency they emit is the same as the working frequency of mobile phones. This will cause enough interference and you will not be able to connect the call to your phone. Currently, there are two types of cell phone jammers available. The first type is usually a small device that can block the signal from a cellular tower to a single cell phone. The blocking frequency is 800MHz to 1900MHz. Most devices using this technology can block signals within a 30-foot radius. Mobile phones in this area do not display signals at all. Now you can politely ask them to leave quietly, or you can buy a cell phone jammer to leave them alone.

https://www.perfectjammer.com/wireless-wifi-bluetooth-jammers.html