Setting up ISP across Islandwide

I am working for an ISP in my country. Currently we are unable to configure our system to stop our clients from logging more than once. Our Clients are unable to log on interstate but they can use the same account to log on in the other states. This is a major problem because the company is losing a lot of money. I have the confidence to get my answers here. I need your help.

Thank you.

Your regards,

Miguel Mundle.

skiguel@hotmail.com