Hi, If I understand you properly you are trying to authenticate users by their mobile phone number.If that's right you need Kannel. You can download the latest version from http://www.kannel.org There is a bit of a learning curve but once you have authenticated the user you can pass them off to your Radius billing system. I presume that the authentication will arrive via SMS, WAP or HTTP if it's 3G. I hope this helps. If you need more advice you can email me at sean@topup.ie Regards, Sean