While an air conditioning recharge is just another way to refer to an air con regas, an air conditioning service is something completely different. The biggest difference between them is the amount of work they include.
During an air con regas, a technician will use a specialised machine to remove the old refrigerant, usually check for any leaks within the system. If all is well, they will then refill the system with the right amount of fresh refrigerant and lubricating oil.
During an air conditioning service, a technician will complete the same recharging process but will give your system a proper inspection. This usually includes:
A full visual system check
Completing a pressure test
Checking that the entire system works properly (all the switches, thermostats etc)
Checking the temperature of the condenser while it is in use
However, this can vary from garage to garage. All these extra checks mean that a service is more expensive than a recharge.