I am relatively new to Freeswitch and I am looking for a way to add isfocus parameter in the Contact header of 200 OK (INVITE response) from the freeswitch. I found channel variable sip_contact_params that can be set in dialplan as below, but it doesnt seem to help. Am I missing something or doing something wrong here?

<action application="answer"/>

<action application="conference" data="..."

Please advise.

Thanks

Ramesh