To chase them: Look for places with phone lines and internet service. Very easy. Look for many calls only outgoing on phone lines.
Listen to the calls (remember, on those places the phone company still operated by goverment agencies)
To avoid them: Get the internet service on one building, send them via radio to another .
Use GSM gateways, where the phone calls are sent out via cellular network.
Use gateways that have many GSM SIMS cards per channel. The machine uses diferent SIM cards on every call, making very dificult to trace the calls. Looks like 300 cell phones making calls on diferent cities, but is only few gateways that get the sims changed every few hours.
Pray like hell that they do not catch you. Some places are outright nasty if you get caught.
Minimun they confiscate the equipment and whatever else they could get.