In first, thanks for your help. I struggle a bit with the rules.
I configured this:
wan - PPPoE provider
wan2 - 2nd provider gives me LAN with static IP
sim1 - Data sim
I configured failover, this is working fine. All Clients ware using the PPPoE line, whan this goes down they go to the LAN and at least, is this ist down, the go to LTE.

Now I make a VoIP rule where two internal IPs (192.168.200.161 and 162) shoud user wan2.
This is also working, i have my load "balanced" data on wan, VoIP on wan2, fine as well :-)

But now I cant configure that when wan2 goes down VoIP shoud use wan and possibly sim.
When I add wan to "member used" the VoIP machines use directly the wan, not the wan2.
Is there an option to configure a seperate failover in a rule ??
Regards, Dirk