Asterisk + freepbx

Hi, i currently have asterisk 10 with freepbx 2.10 with GUI interface. At present asterisk writes all CDR to the master_csv file. The problem i am having is that the source CLID is showing as the extension number whenever a person makes an outbound call, i need to have this set as the outbound CID details as my billing system rates calls based on outbound CID customer has been given. To summarize Source CID of outbound call needs to show as outbound CID specified in users extension Not so that extension number shows as source on any outbound calls. I hope someone has tackled this issue before with ease. i did originally set a Trixbox system like this years ago but forget how i stumbled across doing it.