Sip caller id

I am dialing out to a sip provider on an asterisk 1.4 box. I set the callerid in the context of the sip provider. The caller-id seems to be overridden with the caller id of the x-lite phone, instead. I prefer NOT to set the caller-id in the dialplan, if possible.

Is there a parameter somewhere I can set which will override the caller-id of the internal extension, and override it with the callerid of the outbound context?