[BjörnJ]

http://www.thewirelessfaq.com/are_th...ers_for_mobile

User Recognition

If configured the Openwave gateway might send you one of the following headers: * x-up-subno, a unique identifier for users. Depending on the configuration might be unique or limited to the user-session. * x-up-calling-line-id, this is the user’s full phone number

In most cases, to have these values set you will need to have an agreement with the mobile operator. Not all operators might be able to provide this information in this format through their gateway.