this is a try for an provider template for 3cx v20 to connect to a FritzBox with special settings
following: https://www.youtube.com/watch?v=IRWZ7Ev4yYU (thanks at this point), I modified the following
<!--<field name="ParameterOut" custom="" parameter="ContactUser">$OutboundCallerId</field>-->
<field name="ParameterOut" custom="" parameter="ContactUser">$AuthID</field>
<!--<field name="ParameterOut" custom="" parameter="FromDisplayName">$OutboundCallerId</field>-->
<field name="ParameterOut" custom="" parameter="FromDisplayName">$OriginatorCallerId</field>
<!--<field name="ParameterOut" custom="" parameter="FromUserPart">$OutboundCallerId</field>-->
<field name="ParameterOut" custom="" parameter="FromUserPart">$AuthID</field>
and I added this to the header section of an exported GenericVoIPP.pv.xml GenericVoIPProvider.pv.xml