IAX registration restrictions

I am looking for a solution to restrict the amount of times an IAX client can register to our server. We have clients that are trying to use the same credentials at two separate locations at the same time. We want them to use one set of credentials per login. Right now I see two IAX peers logged into the same conference. Right now I’m manually booting them from the server and telling them our policy.

I would like to see if there is a way to block multiple registrations for a username and password for an IAX user. This way each connection to the server carries it’s own IAX username and password. This would help keep our billing straight, and stop the multiple “registered iax2 “xxx”” I get on the console.

I have searched high and low to try and find a solution for this, but have found nothing.

Thank you in advance.