<user id="pbxuser">
<params>
<param name="password" value="PwgEn123"/>
</params>
<variables>
<variable name="toll_allow" value="domestic,international,local"/>
<variable name="accountcode" value="1000"/>
<variable name="user_context" value="mypbx"/>
<variable name="callgroup" value="techsupport"/>
<variable name="sip-force-expires" value="180"/>
<variable name="sip-force-contact" value="NDLB-connectile-dysfunction"/>
<variable name="nat-options-ping" value="true"/>
</variables>
</user>
But freeswitch does not send option to registered endpoint.