This bill, known as the "END CELLS Act," amends the Communications Act of 1934 to strengthen prohibitions against the unauthorized use of wireless communication devices in detention facilities. It makes it unlawful for any person to provide or attempt to provide such devices to incarcerated individuals, or to knowingly facilitate their introduction into these facilities. The legislation also prohibits individuals held in detention facilities from possessing or attempting to obtain these devices. To deter these actions, the bill establishes enhanced penalties, including a civil forfeiture penalty of up to $50,000 per violation, with a maximum of $1,000,000 for continuing violations. Additionally, a criminal fine of up to $50,000 per violation can be imposed, supplementing existing imprisonment provisions. The bill defines "detention facility" as any correctional, detention, or penal facility within the United States, and "wireless communications device" broadly to include any device enabling radio communication or its network-connecting components. These provisions are intended to apply to conduct occurring after the bill's enactment, without affecting lawful law enforcement activities or state authority to enforce their own laws.