All of the Unusual Pokemon have high human intelligence and most can use cellphones and other tech.
This Unusual Steenee is talkin' too da gurls on her 6G 2TB international call availability phone about some of the human trainers they either scared away or captured. The Unusual Pokemon who use cellphones or the internet aren't going through a service provider, nor are they stealing it from anyone so it's unknown how they're getting full service through their phones and tech with the exception of hints leading towards Arceus providing them their service.