Phones? Easy peasy!
Femtocells controlled by the prison authorities, with a list of authorized IMSIs. Temporary visitors can obtain a short lived authorization -a few hours- so they can communicate with the exterior in an emergency. Add a network of directional detectors to immediately pinpoint unauthorized calls so the wardens can immediately identify any intern trying to make a call, possibly with the help of the prisons surveillance cameras. This should be balanced by inexpensive 'controlled' landline calls so the interns can call their families at a reasonable prize.
The drones? Birds of prey trained to attack drones, helped by a network of directional detectors in the outer walls looking for the frequencies used for controlling drones, detecting their place of origin and probably interfering with the control signals. For drones controlled by mobile phones, see the first paragraph.