[Freeswitch-users] SIP Invite Contact Header

HI All, Hopefully a quick question here. I'm trying to get TLS working with one of our gateway providers and they are asking that I pass an FQDN instead of the external IP address of our Freeswitch server in our contact header within our sip invite. I've tried setting sip_contact_user but that doesn't seem to have any effect on the contents of the contact header. Plus I would really prefer to set this in the gateway profile so it only effects calls passing over a single gateway. Anyone have any advice on how this can be achieved? Thanks Rob