On the good-news side of the equation, Uncle Charlie does not take kindly to people deliberately jamming the airwaves, and they have a long history of meting out serious fines and punishments for violators. With luck, the idiot who ran this will be given years of prison time to serve as a warning to other anti-5G people with similar ideas.
Oh, and to any anti-5G people who may be reading this: radio emissions follow the Inverse Square Law, which means the closer you are to a transmitter, the more RF you are exposed to. A jammer in the same house as you exposes you to far more powerful radiation* than you could possibly get from a nearby cell tower.
As a bonus, if you’re the type who believes “cell phone radiation causes health issues,” a jammer emits signals on a wider band of frequencies than an ordinary transmitter. In the unlikely event you are physiologically capable of having an adverse reaction to a low power signal at a specific frequency, a jammer is far more likely to emit the bad frequency than a controlled transmitter.
* Non-ionizing radiation, which is not the same thing as nuclear radiation.
EDIT Inverse Square Law, not Inverse Cube Law.