HOW WILL I SET IT UP SO THAT CUSTOMERS CAN USE THEY REMAINING TIME WITHOUT CALLING ME TO ADD BACK THERE REMAINING TIME..........

i assume you are using mikrotik hotspot? radius authentication? just set the idle timeout in WinBox GOTO: IP>HOTSPOT>SERVERS Tab select the default server or the one your are using input value (idle timeout 5:00) once the client has disconnected for a period of 5min the session will be terminated and unused time / credit will be available to use if the account has not expired due to expiry date!

Cheers Paul.